Rotating compensator ellipsometer system with spatial filter

ABSTRACT

Disclosed is the application of spatial filter(s) in rotating compensator ellipsometer systems prior to or after a sample system. The purpose is, for instance, to eliminate a radially outer annulus of a generally arbitrary Profile beam that presents with low intensity level irregular content, so that electromagnetic beam intensity is caused to quickly decay to zero as a function of radius.

This Application claims the benefit of Ser. Nos. 60/207,537 filed May26, 2000; 60/039,519, filed Mar. 3, 1997 and Ser. No. 60/042,661, filedApr. 4, 1997. This Application is further a CIP of Co-Pendingapplication Ser. No. 09/496,011 Filed Feb. 1, 2000, which depended fromof application Ser. No. 09/246,888 filed Feb. 8, 1999, (now U.S. Pat.No. 6,084,675). Further, via the application Ser. No. 09/246,888 thisand Application is a Continuation-In-Part of CIP from application Ser.No. 08/912,211 filed Aug. 15, 1997, (now U.S. Pat. No. 5,872,630), whichwas a CIP from application Ser. No. 08/530,892 filed Sep. 20, 1995, (nowU.S. Pat. No. 5,666,201); and is a CIP of application Ser. No.08/618,820 filed Mar. 20, 1996, (now U.S. Pat. No. 5,706,212). ThisApplication is further a CIP of Co-Pending applications Ser. Nos.09/225,118 filed Jan. 4, 1999, (now U.S. Pat. No. 6,084,674); and09/223,8224 filed Jan. 4, 1999, (now U.S. Pat. No. 6,118,537); Ser. No.09/232,257 filed Jan. 19, 1999, (now U.S. Pat. No. 6,141,102); Ser. No.09/225,371 filed Jan. 4,1999 now U.S. Pat. No. 6,100,981); Ser. No.09/225,076 filed Jan. 4, 1999 which is a continuing of Co-PendingApplications depend from application Ser. No. 08/997,311 filed Dec. 23,1997, now U.S. Pat. No. 5,946,098. In addition, priority is Claimed frompatent application Ser. No. 09/162,217 filed Sep. 29, 1998, (now U.S.Pat. No. 6,034,777).

TECHNICAL FIELD

The present invention relates to rotating compensator ellipsometersystems, and more particularly to spectroscopic rotating compensatorellipsometer systems which comprise spatial filters before and/or afteran investigated sample system.

BACKGROUND

Not limited to, but particularly in the case where an electromagneticbeam is utilized to investigate a sample system which presents with avarying depth surface topology, it is important to provide anelectromagnetic beam of a known lateral dimension and which presentswith a relatively simple cross-sectional intensity profile.

It is noted that often electromagnetic beams present with asubstantially arbitrary intensity profile, with the highest intensitybeing located centrally, which intensity generally decreasing as withincreasing radius. While an arbitrary beam intensity profile istypically acceptable for use in ellipsometry and related practices, ithas been found that once the intensity of a substantially arbitraryprofile beam of electromagnetic radiation has decreased to, as anarbitrary example, say 10% of its peak, it does not always continue todecay directly to essentially zero (0.0). Instead, it often presentsirregularly as a function of radius, (eg. easily visualized as beinggenerally similar to the Fourier transform of a square wave), and suchirregular intensity content can adversely affect ellipsometerperformance. The cause of said irregular intensity profile can includesuch as optical element wavelength dependent diffraction, surfaceroughness or other non-idealities, and where electromagnetic radiationis provided via an aperture or via the end of a light fiber contained ina cladding, electromagnetic radiation falling outside a geometric imagethereof is often of an irregular intensity content.

It would be of benefit, as regards obtaining accurate data fromapplication of ellipsometers and the like systems, if the intensity ofan electromagnetic beam could be forced to decay quickly to zero (0.0),rather than demonstrate an irregular intensity profile as a function ofradius in an outer annulus region.

With an eye to the present invention, a Search of Patents was conducted.Perhaps the most relevant Patent identified is U.S. Pat. No. 5,517,312to Finarov. Said 312 Patent describes application of a scattered lightreducing system at the entry to a Detector in a Rotating Analyzer orRotating Polarizer Ellipsometer System, which scattered light reducingsystem consists of two lenses with a pin-hole containing diaphramlocated midway therebetween, and at the focal lengths of said lenses.Said scattered light reducing system is present after a sample systemand processes electromagnetic radiation after it interacts with saidsample system. The pinhole is described as serving to reduce scatteredlight and providing high spatial resolution. Another Patent identifiedis that to Campbell et al., U.S. Pat. No. 5,148,323. Said 323 Patentdescribes a Spatial Filter in which a pinhole is located other than atthe focal length of a converging lens. U.S. Pat. No. 3,905,675 toMcCraken describes a Spatial Filter containing system which enablesobservation of a weak source of electromagnetic radiation in thepresence of strong sources thereof. U.S. Pat. No. 5,684,642 to Zumoto etal., describes an optical transmission system for use in fashioning anelectromagnetic beam for use in machining materials which combines aSpatial Filter and an Optical Fiber. U.S. Pat. No. 4,877,960 toMesserschmidt et al. is identified as it describes masking energy fromoutside the target area in a microscope having dual remote imagemasking.

Continuing, Spectroscopic Rotating Compensator Ellipsometer Systems arealso known in the art. And, as mentioned, application a Spatial Filtersnear a Detector, in the context of Rotating Polarizer and RotatingAnalyzer Ellipsometer Systems has been reported, (see U.S. Pat. No.5,517,312 to to Finerov). However, the application of Spatial Filters inRotating Compensator Ellipsometer Systems, such as the RotatingCompensator Ellipsometer System Claimed in co-owned U.S. Pat. No.5,872,630, has not here-to-fore been known. Said 630 Patent, which isincorporated by reference hereinto and which is co-owned with thisApplication, is disclosed as it describes an ellipsometer system inwhich an analyzer and polarizer are maintained in a fixed in positionduring data acquisition, while at least one compensator is caused tocontinuously rotate.

A Patent to Dill et al., U.S. Pat. No. 4,053,232 is disclosed as itdescribes a Rotating-Compensator Ellipsometer System which operatesutilizing monochromatic light.

A Patent to Aspnes et al., U.S. Pat. No. 5,877,859 is disclosed as itdescribes a Broadband Spectroscopic Rotating Compensator EllipsometerSystem wherein the Utility is derived from selecting a wavelength rangeand compensator so that at least one wavelength in said wavelength rangehas a retardation imposed of between 135 and 225 degrees, and anotherwavelength in said wavelength range has a retardation imposed which isoutside that retardation range.

A Patent, U.S. Pat. No. 5,329,357 to Bernoux et al. is also identifiedas it Claims use of fiber optics to carry electromagnetic radiation toand from an ellipsometer system which has at least one polarizer oranalyzer which rotates during data acquisition. It is noted that if boththe polarizer and analyzer are stationary during data acquisition thatthis Patent is not controlling where electromagnetic radiation carryingfiber optics are present.

Further Patents of general interest of which the Inventors are awareinclude those to Woollam et al, U.S. Pat. No. 5,373,359, Patent to Johset al. U.S. Pat. No. 5,666,201 and Patent to Green et al., U.S. Pat. No.5,521,706, and Patent to Johs et al., U.S. Pat. No. 5,504,582 aredisclosed for general information as they pertain to ellipsometersystems.

A Patent to He et al., U.S. Pat. No. 5,963,327 is also disclosed as itdescribes a laterally compact ellipsometer system which enablesproviding a polarized beam of electromagnetic radiation at an obliqueangle-of-incidence to a sample system in a small spot area.

In addition to the identified Patents, certain Scientific papers arealso identified.

A paper by Johs, titled “Regression Calibration Method for RotatingElement Ellipsometers”, Thin Solid Films, 234 (1993) is also disclosedas it describes a mathematical regression based approach to calibratingellipsometer systems.

A Review paper by Collins, titled “Automatic Rotating ElementEllipsometers: Calibration, Operation and Real-Time Applications”, Rev.Sci. Instrum., 61(8) (1990), is identified for general information.

Even in view of the known art, in the context of rotating compensatorellipsometer systems, a need remains for a system and methodology of itsuse, which adds spatial filter means before and/or after a sample sytem,to, for instance, fashion a beam with a radially essentially arbitraryProfile which directly approaches zero intensity. The present inventionmeets said need.

DISCLOSURE OF THE INVENTION

Rotating Compensator Ellipsometer Systems provide many benefits, (eg.Sample System PSI and DELTA investigation limiting “dead-spots” are notpresent), but until a co-owned Patent to Johs et al., U.S. Pat. No.5,872,630 taught otherwise, it was generally believed that in theabsence of essentially Achromatic “ideal” Compensators, it would beprohibitively difficult and expensive to build, calibrate and utilize a“Spectroscopic” Rotating Compensator Ellipsometer System. This is to beunderstood in light of the fact that Compensators which are essentiallyAchromatic, (ie. provide essentially constant retardation over a largerange of Wavelengths, such as 190-1000 nanometers), are not generallyand economically available as off-the-shelf items. The present inventionexpands on the utility available from the Spectroscopic RotatingCompensator Ellipsometer System previously taught in the 630 Patent. Invery general terms the present invention is a rotating compensatorellipsometer system which generates an electromagnetic beam and causesit to impinge upon a sample system, said spectroscopic rotatingcompensator ellipsometer system comprising, prior to and/or after saidsample system, at least one spatial filter which, for instance, servesto attenuate an outer annular region from said electromagnetic beam asit passes therethrough. More specifically, the present inventionspectroscopic rotating compensator ellipsometer system is affordable,easy to calibrate and utilize and comprises a Source of a PolychromaticBeam of Electromagnetic Radiation, a Polarizer, a Stage for Supporting aSample System, an Analyzer, a Dispersive Optics and at least one PhotoArray Detector Element System which contains a multiplicity of DetectorElements, which Spectroscopic Rotating Compensator System furthercomprises at least one Rotatable Compensator(s) positioned atlocation(s) selected from the group consisting of:

(before said stage for supporting a sample system and after said stagefor supporting a sample system and both before and after said stage forsupporting a sample system). Said present invention SpectroscopicRotating Compensator Ellipsometer System also comprises a Spatial FilterSystem which minimally sequentially comprises:

beam converging at least one lens and/or mirror;

diaphram with a pin hole therein located near the focal length of saidbeam converging at least one lens and/or mirror; and

beam collimating at least one lens and/or mirror;

such that in use an electromagnetic beam which is caused to interactwith said beam converging at least one lens and/or mirror becomesfocused on, and at least partially passes through said pin hole in saiddiaphram, and then becomes recollimated by said second beam at least onecollimating lens and/or mirror.

A preferred present invention spectroscopic rotating compensator basedellipsometer system comprises addition of an aperture such that theconfiguration is:

first beam collimating lens;

aperture;

first beam converging at least one lens and/or mirror;

diaphram with a pin hole therein located essentially at the focal lengthof said beam converging at least one lens and/or mirror; and

second beam collimating at least one lens and/or mirror;

and such that, in use, the central portion of the electromagnetic beamwhich is collimated by said first beam collimating lens is caused topass through said aperture, become focused on and at least partiallypass through said pin hole in said diaphram by said first beamconverging at least one lens and/or mirror, and become recollimated bysaid second beam collimating at least one lens and/or mirror.

The present invention can also be considered to be a spectroscopicrotating compensator based ellipsometer system which comprises:

a polarization state generator comprising said Source of a PolychromaticBeam of Electromagnetic Radiation and Polarizer;

means for supporting a sample system; and

a polarization state detector, comprising said Analyzer, a DispersiveOptics and at least one Photo Array Detector Element System whichcontains a multiplicity of Detector Elements;

with at least one of said polarization state generator and polarizationstate detector further comprising at least one compensator;

and a spatial filter being present in at least one selection from thegroup consisting of:

said polarization state generator; and

said polarization state detector;

which spatial filter which sequentially comprises:

first at least one lens and/or mirror;

pin hole containing diaphram; and

second at least one lens and/or mirror;

with the optional inclusion of

collimating lens;

aperture;

prior to said first at least one lens and/or mirror;

said pin hole containing diaphram being positioned near the focal pointsof said first and second at least one lenses or mirrors, such that acollimated electromagnetic beam enters said first at least one lens ormirror, is converged and at least partially passes through said pinhole, and is recollimated by said second at least one lens and/ormirror. Spatial filter(s) can be present in either the polarizationstate generator or polarization detector. Said spatial filter can bepositioned at a location selected from the group consisting of:

between the source of electromagnetic radiation and the polarizer;

between a compensator and sample system;

between the sample system and a compensator;

between a compensator and analyzer; and

between the analyzer and detector.

The present invention is further, in the context of spectroscopicrotating compensator based ellipsometer systems, a method of processingelectromagnetic beams to, for instance, eliminate a radially outerannulus thereof, said outer annulus often being comprised of lowintensity level irregular content, said method comprising placing atleast one spatial filter(s) such that said electromagnetic beam passestherethrough, each present spatial filter sequentially comprising:

aperture;

beam converging at least one lens and/or mirror;

diaphram with a pin hole therein located near the focal length of saidbeam converging at least one lens and/or mirror; and

beam collimating at least one lens and/or mirror;

such that, in use, an electromagnetic beam which is caused to passthrough said aperture, become focused on and at least partially passthrough said pin hole in said diaphram by said beam converging at leastone lens and/or mirror, and become recollimated by said second beamcollimating at least one lens and/or mirror.

Said present invention method can be recited as, in the context of aspectroscopic rotating compensator ellipsometer system which causes abeam of electromagnetic radiation to interact with a sample system,comprising the steps of:

a. providing a beam of electromagnetic radiation;

b. providing a sample system;

c. placing at least one spatial filter(s) in the pathway of saidelectromagnetic beam such that said electromagnetic beam passestherethrough prior to or after said electromagnetic beam being caused tointeract with a sample system;

the purpose being to, for instance, eliminate a radially outer annulusof said electromagnetic beam which is comprised of a low intensity levelirregular content.

In the preferred present invention Rotating Compensator EllipsometerSystem, said at least one Compensator(s) utilized in the presentinvention can be essentially any available, reasonably priced,off-the-shelf Retardation providing system, including non-Achromatic,Berek-type, Zero-Order Waveplate, Multiple-Order Waveplate, Combinationsof Multiple-Order Waveplates, Polymer Retarder, Mica Waveplate, FreshnelRhomb, Achromatic, and Pseudo-Achromatic, etc.

For general information, it is noted that a Berek-type Compensator is auniaxially anisotropic plate of material in which the Optical Axis isoriented perpendicularly to a plate surface thereof. When a PolarizedBeam of Electromagnetic Radiation is caused to be incident other thanalong the Optical Axis, orthogonal components thereof encounterdifferent effective Indicies of Refraction, thereby effectingretardation therebetween. A Zero-Order Quartz Waveplate is typicallyconstructed by combining two Multi-Order (Quartz) Waveplates which haveOptical Axes oriented at ninety (90) degrees with respect to oneanother. The two Multi-Order waveplates are selected so that thedifference in retardation entered by each gives rise to an overallZero-Order retardance characteristic. Polymer Compensators are made of apolymer material and can provide true Zero-Order retardance which, as domany Compensators, provides an inverse wavelength functional RetardanceCharacteristic. Essentially Achromatic (Pseudo-Achromatic) Compensatorscan be constructed by stacking appropriately chosen Polymer and Crystalwaveplates. A potential advantage of said essentially AchromaticCompensators is that Retardance can be essentially constant over a rangeof wavelengths.

While it is known that generally available Compensators do not providean exact Ninety (90) Degrees of Retardation at all wavelengths over arelatively large range of Wavelengths, the present invention, asdescribed later herein, utilizes a Regression based Calibrationprocedure which compensates for said non-ideal Compensator Retardationcharacteristics. And while it is true that the sensitivity and accuracyof a Rotating Compensator System degrades as the Retardance provided bya utilized Compensator approaches zero (0.0) or one-hundred-eighty (180)degrees, it has been found that Compensators which demonstrateRetardation, over a range of utilized Wavelengths, of from forty (40) toone-hundred-seventy (170) degrees, are acceptable for use in the presentinvention, and allow achieving very impressive results over ademonstrated relatively large range of wavelengths, (eg. at leasttwo-hundred-fifty (250) to one-thousand (1000) nanometers).

When the present invention Spectroscopic Rotating CompensatorEllipsometer System is used to investigate a Sample System present onsaid Stage for Supporting a Sample System, said Analyzer and Polarizerare maintained essentially fixed in position and at least one of said atleast one Compensator(s) is/are caused to continuously rotate while aPolychromatic Beam of Electromagnetic Radiation produced by said Sourceof a Polychromatic Beam of Electromagnetic Radiation is caused to passthrough said Polarizer and said Compensator(s). Said Polychromatic Beamof Electromagnetic Radiation is also caused to interact with said SampleSystem, pass through said Analyzer and interact with said DispersiveOptics such that a Multiplicity of Essentially Single Wavelengths arecaused to simultaneously enter a corresponding multiplicity of DetectorElements in said Detector System Photo Array.

While the present invention can utilize essentially any Compensator, apreferred embodiment of the present invention provides that at least oneof said at least one compensator(s) which is mounted to rotate about thelocus of a beam of electromagnetic radiation caused to passtherethrough, be selected from the group consisting of:

a single element compensator;

a compensator system comprised of at least two per se. zero-orderwaveplates, said per se. zero-order waveplates having their respectivefast axes rotated to a position offset from zero or ninety degrees withrespect to one another, with a nominal value being forty-five degrees;

a compensator system comprised of a combination of at least a first anda second effective zero-order wave plate, said first effectivezero-order wave plate being comprised of two multiple order waveplateswhich are combined with the fast axes thereof oriented at a nominalninety degrees to one another, and said second effective zero-order waveplate being comprised of two multiple order waveplates which arecombined with the fast axes thereof oriented at a nominal ninety degreesto one another; the fast axes and of the multiple order waveplates insaid second effective zero-order wave plate being rotated to a positionat a nominal forty-five degrees to the fast axes, respectively, of themultiple order waveplates in said first effective zero-order waveplate;

a compensator system comprised of a combination of at least a first anda second effective zero-order wave plate, said first effectivezero-order wave plate being comprised of two multiple order waveplateswhich are combined with the fast axes thereof oriented at a nominalninety degrees to one another, and said second effective zero-order waveplate being comprised of two multiple order waveplates which arecombined with the fast axes thereof oriented at a nominal ninety degreesto one another; the fast axes of the multiple order waveplates in saidsecond effective zero-order wave plate being rotated to a position awayfrom zero or ninety degrees with respect to the fast axes, respectively,of the multiple order waveplates in said first effective zero-orderwaveplate;

a compensator system comprised of at least one zero-order waveplate, andat least one effective zero-order waveplate, said effective zero-orderwave plate, being comprised of two multiple order waveplates which arecombined with the fast axes thereof oriented at a nominal ninety degreesto one another, the fast axes of the multiple order waveplates in saideffective zero-order wave plate, being rotated to a position away fromzero or ninety degrees with respect to the fast axis of the zero-orderwaveplate;

as are shown in FIGS. 5a-5 e.

Additional compensator systems, as shown in FIGS. 5f-5 m, which werepreviously disclosed in patent application Ser. No. 08/997,311, (nowU.S. Pat. No. 5,946,098), and CIP's therefrom, and which arespecifically within the scope of the invention and can be included inthe selection group are:

a compensator system comprised of a first triangular shaped element,which as viewed in side elevation presents with first and second sideswhich project to the left and right and downward from an upper point,which first triangular shaped element first and second sides havereflective outer surfaces; said retarder system further comprising asecond triangular shaped element which as viewed in side elevationpresents with first and second sides which project to the left and rightand downward from an upper point, said second triangular shaped elementbeing made of material which provides reflective interfaces on first andsecond sides inside thereof; said second triangular shaped element beingoriented with respect to the first triangular shaped element such thatthe upper point of said second triangular shaped element is orientedessentially vertically directly above the upper point of said firsttriangular shaped element; such that in use an input electromagneticbeam of radiation caused to approach one of said first and second sidesof said first triangular shaped element along an essentiallyhorizontally oriented locus, is caused to externally reflect from anouter surface thereof and travel along a locus which is essentiallyupwardly vertically oriented, then enter said second triangular shapedelement and essentially totally internally reflect from one of saidfirst and second sides thereof, then proceed along an essentiallyhorizontal locus and essentially totally internally reflect from theother of said first and second sides and proceed along an essentiallydownward vertically oriented locus, then externally reflect from theother of said first and second sides of said first triangular shapedelements and proceed along an essentially horizontally oriented locuswhich is undeviated and undisplaced from the essentially horizontallyoriented locus of said input beam of essentially horizontally orientedelectromagnetic radiation even when said retarder is caused to rotate;with a result being that retardation is entered between orthogonalcomponents of said input electromagnetic beam of radiation;

a compensator system comprised of, as viewed in upright side elevation,first and second orientation adjustable mirrored elements which eachhave reflective surfaces; said compensator/retarder system furthercomprising a third element which, as viewed in upright side elevation,presents with first and second sides which project to the left and rightand downward from an upper point, said third element being made ofmaterial which provides reflective interfaces on first and second sidesinside thereof; said third element being oriented with respect to saidfirst and second orientation adjustable mirrored elements such that inuse an input electromagnetic beam of radiation caused to approach one ofsaid first and second orientation adjustable mirrored elements along anessentially horizontally oriented locus, is caused to externally reflecttherefrom and travel along a locus which is essentially upwardlyvertically oriented, then enter said third element and essentiallytotally internally reflect from one of said first and second sidesthereof, then proceed along an essentially horizontal locus andessentially totally internally reflect from the other of said first andsecond sides and proceed along an essentially downward verticallyoriented locus, then reflect from the other of said first and secondorientation adjustable mirrored elements and proceed along anessentially horizontally oriented propagation direction locus which isessentially undeviated and undisplaced from the essentially horizontallyoriented propagation direction locus of said input beam of essentiallyhorizontally oriented electromagnetic radiation even when saidcompensator/retarder is caused to rotate; with a result being thatretardation is entered between orthogonal components of said inputelectromagnetic beam of radiation;

a compensator system comprised of a parallelogram shaped element which,as viewed in side elevation, has top and bottom sides parallel to oneanother, both said top and bottom sides being oriented essentiallyhorizontally, said retarder system also having right and left sidesparallel to one another, both said right and left sides being orientedat an angle to horizontal, said retarder being made of a material withan index of refraction greater than that of a surrounding ambient; suchthat in use an input beam of electromagnetic radiation caused to enter aside of said retarder selected from the group consisting of: (right andleft), along an essentially horizontally oriented locus, is caused todiffracted inside said retarder system and follow a locus which causesit to essentially totally internally reflect from internal interfaces ofboth said top and bottom sides, and emerge from said retarder systemfrom a side selected from the group consisting of (left and rightrespectively), along an essentially horizontally oriented locus which isundeviated and undisplaced from the essentially horizontally orientedlocus of said input beam of essentially horizontally orientedelectromagnetic radiation even when said retarder is caused to rotate;with a result being that retardation is entered between orthogonalcomponents of said input electromagnetic beam of radiation;

a compensator system comprised of first and second triangular shapedelements, said first triangular shaped element, as viewed in sideelevation, presenting with first and second sides which project to theleft and right and downward from an upper point, said first triangularshaped element further comprising a third side which is orientedessentially horizontally and which is continuous with, and present belowsaid first and second sides; and said second triangular shaped element,as viewed in side elevation, presenting with first and second sideswhich project to the left and right and upward from an upper point, saidsecond triangular shaped element further comprising a third side whichis oriented essentially horizontally and which is continuous with, andpresent above said first and second sides; said first and secondtriangular shaped elements being positioned so that a rightmost side ofone of said first and second triangular shaped elements is in contactwith a leftmost side of the other of said first and second triangularshaped elements over at least a portion of the lengths thereof; saidfirst and second triangular shaped elements each being made of materialwith an index of refraction greater than that of a surrounding ambient;such that in use an input beam of electromagnetic radiation caused toenter a side of a triangular shaped element selected from the groupconsisting of: (first and second), not in contact with said othertriangular shape element, is caused to diffracted inside said retarderand follow a locus which causes it to essentially totally internallyreflect from internal interfaces of said third sides of each of saidfirst and second triangular shaped elements, and emerge from a side ofsaid triangular shaped element selected from the group consisting of:(second and first), not in contact with said other triangular shapeelement, along an essentially horizontally oriented locus which isundeviated and undisplaced from the essentially horizontally orientedlocus of said input beam of essentially horizontally orientedelectromagnetic radiation even when said retarder is caused to rotate;with a result being that retardation is entered between orthogonalcomponents of said input electromagnetic beam of radiation;

a compensator system comprised of a triangular shaped element, which asviewed in side elevation presents with first and second sides whichproject to the left and right and downward from an upper point, saidretarder system further comprising a third side which is orientedessentially horizontally and which is continuous with, and present belowsaid first and second sides; said retarder system being made of amaterial with an index of refraction greater than that of a surroundingambient; such that in use a an input beam of electromagnetic radiationcaused to enter a side of said retarder system selected from the groupconsisting of: (first and second), along an essentially horizontallyoriented locus, is caused to diffracted inside said retarder system andfollow a locus which causes it to essentially totally internally reflectfrom internal interface of said third sides, and emerge from saidretarder from a side selected from the group consisting of (second andfirst respectively), along an essentially horizontally oriented locuswhich is undeviated and undisplaced from the essentially horizontallyoriented locus of said input beam of essentially horizontally orientedelectromagnetic radiation even when said retarder system is caused torotate; with a result being that retardation is entered betweenorthogonal components of said input electromagnetic beam of radiation;and

a compensator system comprised of first and second Berek-type retarderswhich each have an optical axes essentially perpendicular to a surfacethereof, each of which first and second Berek-type retarders has a fastaxis, said fast axes in said first and second Berek-type retarders beingoriented in an orientation selected from the group consisting of:(parallel to one another and other than parallel to one another); saidfirst and second Berek-type retarders each presenting with first andsecond essentially parallel sides, and said first and second Berek-typeretarders being oriented, as viewed in side elevation, with first andsecond sides of one Berek-type retarder being oriented other thanparallel to first and second sides of the other Berek-type retarder;such that in use an incident beam of electromagnetic radiation is causedto impinge upon one of said first and second Berek-type retarders on oneside thereof, partially transmit therethrough then impinge upon thesecond Berek-type retarder, on one side thereof, and partially transmittherethrough such that a polarized beam of electromagnetic radiationpassing through both of said first and second Berek-type retardersemerges from the second thereof in a polarized state with a phase anglebetween orthogonal components therein which is different than that inthe incident beam of electromagnetic radiation, and in a propagationdirection which is essentially undeviated and undisplaced from theincident beam of electromagnetic radiation even when said retardersystem is caused to rotate; with a result being that retardation isentered between orthogonal components of said input electromagnetic beamof radiation;

a compensator system comprised of first and second Berek-type retarderswhich each have an optical axes essentially perpendicular to a surfacethereof, each of which first and second Berek-type retarders has a fastaxis, said fast axes in said first and second Berek-type retarders beingoriented other than parallel to one another; said first and secondBerek-type retarders each presenting with first and second essentiallyparallel sides, and said first and second Berek-type retarders beingoriented, as viewed in side elevation, with first and second sides ofone Berek-type retarder being oriented other than parallel to first andsecond sides of the other Berek-type retarder; such that in use anincident beam of electromagnetic radiation is caused to impinge upon oneof said first and second Berek-type retarders on one side thereof,partially transmit therethrough then impinge upon the second Berek-typeretarder, on one side thereof, and partially transmit therethrough suchthat a polarized beam of electromagnetic radiation passing through bothof said first and second Berek-type retarders emerges from the secondthereof in a polarized state with a phase angle between orthogonalcomponents therein which is different than that in the incident beam ofelectromagnetic radiation, and in a propagation direction which isessentially undeviated and undisplaced from the incident beam ofelectromagnetic radiation, said spectroscopic ellipsometer/polarimetersystem further comprising third and fourth Berek-type retarders whicheach have an optical axes essentially perpendicular to a surfacethereof, each of which third and fourth Berek-type retarders has a fastaxis, said fast axes in said third and fourth Berek-type retarders beingoriented other than parallel to one another, said third and fourthBerek-type retarders each presenting with first and second essentiallyparallel sides, and said third and fourth Berek-type retarders beingoriented, as viewed in side elevation, with first and second sides ofone of said third and fourth Berek-type retarders being oriented otherthan parallel to first and second sides of said fourth Berek-typeretarder; such that in use an incident beam of electromagnetic radiationexiting said second Berek-type retarder is caused to impinge upon saidthird Berek-type retarder on one side thereof, partially transmittherethrough then impinge upon said fourth Berek-type retarder on oneside thereof, and partially transmit therethrough such that a polarizedbeam of electromagnetic radiation passing through said first, second,third and fourth Berek-type retarders emerges from the fourth thereof ina polarized state with a phase angle between orthogonal componentstherein which is different than that in the incident beam ofelectromagnetic radiation caused to impinge upon the first side of saidfirst Berek-type retarder, and in a direction which is essentiallyundeviated and undisplaced from said incident beam of electromagneticradiation even when said retarder system is caused to rotate; with aresult being that retardation is entered between orthogonal componentsof said input electromagnetic beam of radiation;

a compensator system comprised of first, second, third and fourthBerek-type retarders which each have an optical axes essentiallyperpendicular to a surface thereof, each of which first and secondBerek-type retarders has a fast axis, said fast axes in said first andsecond Berek-type retarders being oriented essentially parallel to oneanother; said first and second Berek-type retarders each presenting withfirst and second essentially parallel sides, and said first and secondBerek-type retarders being oriented, as viewed in side elevation, withfirst and second sides of one Berek-type retarder being oriented otherthan parallel to first and second sides of the other Berek-typeretarder; such that in use an incident beam of electromagnetic radiationis caused to impinge upon one of said first and second Berek-typeretarders on one side thereof, partially transmit therethrough thenimpinge upon the second Berek-type retarder, on one side thereof, andpartially transmit therethrough such that a polarized beam ofelectromagnetic radiation passing through both of said first and secondBerek-type retarders emerges from the second thereof in a polarizedstate with a phase angle between orthogonal components therein which isdifferent than that in the incident beam of electromagnetic radiation,and in a propagation direction which is essentially undeviated andundisplaced from the incident beam of electromagnetic radiation; each ofwhich third and fourth Berek-type retarders has a fast axis, said fastaxes in said third and fourth Berek-type retarders being orientedessentially parallel to one another but other than parallel to the fastaxes of said first and second Berek-type retarders, said third andfourth Berek-type retarders each presenting with first and secondessentially parallel sides, and said third and fourth Berek-typeretarders being oriented, as viewed in side elevation, with first andsecond sides of one of said third and fourth Berek-type retarders beingoriented other than parallel to first and second sides of said fourthBerek-type retarder; such that in use an incident beam ofelectromagnetic radiation exiting said second Berek-type retarder iscaused to impinge upon said third Berek-type retarder on one sidethereof, partially transmit therethrough then impinge upon said fourthBerek-type retarder on one side thereof, and partially transmittherethrough such that a polarized beam of electromagnetic radiationpassing through said first, second, third and fourth Berek-typeretarders emerges from the fourth thereof in a polarized state with aphase angle between orthogonal components therein which is differentthan that in the incident beam of electromagnetic radiation caused toimpinge upon the first side of said first Berek-type retarder, and in adirection which is essentially undeviated and undisplaced from saidincident beam of electromagnetic radiation even when said retardersystem is caused to rotate; with a result being that retardation isentered between orthogonal components of said input electromagnetic beamof radiation.

A present invention spectroscopic rotatable compensator ellipsometersystem can also comprise at least one compensator(s) which produces aretardance of, preferably, between seventy-five (75) andone-hundred-thirty (130) degrees over a range of wavelengths defined bya selection from the group consisting of:

a. between one-hundred-ninety (190) and seven-hundred-fifty (750)nanometers;

b. between two-hundred-forty-five (245) and nine-hundred (900)nanometers;

c. between three-hundred-eighty (380) and seventeen-hundred (1700)nanometers;

d. within a range of wavelengths defined by a maximum wavelength (MAXW)and a minimum wavelength (MINW) wherein the ratio of (MAXW)/(MINW) is atleast one-and-eight-tenths (1.8).

Acceptable practice however, also provides for the case wherein at leastone of said at least one compensator(s) provides a retardation vs.wavelength characteristic retardation between thirty (30.0) and lessthan one-hundred-thirty-five (135) degrees over a range of wavelengthsspecified from MINW to MAXW by a selection from the group consisting of:

a. MINW less than/equal to one-hundred-ninety (190) and MAXW greaterthan/equal to seventeen-hundred (1700);

b. MINW less than/equal to two-hundred-twenty (220) and MAXW greaterthan/equal to one-thousand (1000) nanometers;

c. within a range of wavelengths defined by a maximum wavelength (MAXW)and a minimum wavelength (MINW) range where (MAXW)/(MINW) is at leastfour-and one-half (4.5).

(NOTE, the specified vales and ranges can not be achieved by singleplates with (1/wavelength) retardation characteristics).

The present invention will be better understood by reference to theDetailed Description Section of this Disclosure, in conjunction with theaccompanying Drawings.

SUMMARY OF THE INVENTION

It is therefore a purpose and/or objective of the present invention toprovide, in the context of a rotating compensator ellipsometer sytem, aspatial filter system and method for forming a beam of electromagneticradiation which presents with an intensity profile which radially dropsoff quickly to zero (0.0) without demonstrating low level oscillationssimilar to Fourier Transform of a Square Wave characteristics.

It is another purpose and/or objective of the present invention toteach, either prior to or after a sample system, application of aspatial filter system for forming a beam of electromagnetic radiationwhich, for instance, presents with an intensity profile which drops offquickly to zero (0.0), in spectroscopic rotating compensatorellipsometer systems.

Other purposes and/or objectives of the present invention will becomeobvious from a reading of the Specification and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a 1 shows a basic rotating compensator ellipsometer system aspreviously reported in U.S. Pat. No. 5,872,630.

FIG. 1a 2 shows a general elemental configuration of an ellipsometersystem including a present invention spatial filter.

FIG. 1a 3 shows another general elemental configuration of anellipsometer system including a present invention spatial filter.

FIGS. 1a 4 and 1 a 5 show, in dashed lines, that at least one SpatialFilter (SF) is present at at least one location somewhere in thedemonstrate Rotating Compensator Ellipsometer System.

FIG. 2 shows an example of a source of electromagnetic radiationcomprising a light fiber, lens, apertures and polarizer.

FIG. 3a shows an example of a present invention spatial filter incombination with the system of FIG. 2.

FIG. 3b shows alternative spatial filter construction which can beapplied in the context of a FIG. 2 system.

FIG. 4 shows the effect of the presence of a spatial filter on theradial intensity of an electromagnetic beam as is developed and utilizedin spectroscopic rotating compensator ellipsometers.

FIGS. 5a-5 m show various Compenator designs which can be applied in thepresent invention spectroscopic rotating compensator ellipsometers.

DETAILED DESCRIPTION

Turning now to the Drawings, there is shown in FIG. 1a 1 a basicRotating Compensator Ellipsometer system as disclosed in U.S. Pat. No.5,872,630, demonstrating both reflection and transmission modes, andcomprising a Source of Electromagnetic Radiation (LS), a Polarizer (P),Compensator(s) (C) (C′) (C″), and a Detector (DET). Source (LS) is shownto provide a beam of electromagnetic radiation (PPCLB), and a beam ofelectromagnetic radiation (EPCLB) is shown reflecting from/transmittingthrough a Sample System (SS).

FIG. 1a 2 shows a general elemental configuration of an ellipsometersystem to which the present invention can be applied to investigate asample system (SS). Shown for reflection and transmission are:

a. a Source of a beam electromagnetic radiation (LS);

b. a Polarizer (P);

c. a Compensator (C1);

d. optional additional element(s) (AC1);

e. a sample system (SS);

f. optional additional element(s) (AC2);

g. a Compensator (C2);

h. an Analyzer (A); and

i. a Detector System (DET).

The elements identified as (LS), (P) and (C1) can be considered to form,as a group, a Polarization State Generator (PSG), and the components(C2), (A) and (DET) can be considered, as a group, to form aPolarization State Detector (PSD). It is to be understood that the d.and f. optional “additional elements”, (AC1) and (AC2), can beconsidered as being, for instance, optional input and output lenses orperhaps windows in a vacuum chamber. Also note that after the Polarizer(P) there is indicated, in dashed lines, the presence of a presentinvention Spatial Filter (SF). As better demonstrated in FIGS. 1a 4 and1 a 5, other Spatial Filter (SF) locations in a rotating compensatorellipsometer system, such as prior to the Polarizer (P), after theCompensator (C1) or after the Additional Elements (AC1), or on theDetector (DET) side of the Sample System (SS), before or after theadditional element(s), (AC2); Compensator (C2); and Analyzer (A), areincluded in the scope of the present invention.

Another embodiment of an ellipsometer system to which the presentinvention can be applied is shown in FIG. 1a 3, which shows aPerspective view of a demonstrative system. FIG. 1a 3 shows a LightSource (LS) and a Polarizer (P), which in combination serve to produce agenerally horizontally oriented Polarized Beam of ElectromagneticRadiation (LBI). Said generally horizontally oriented Polarized Beam ofElectromagnetic Radiation (LBI) is caused to interact with OpticalElement, (eg. Prism), (PRI), essentially totally internally reflecttherein, pass through Focusing Optic (F1) and become generallyvertically oriented Polarized Beam of Electromagnetic Radiation (LBI′),then interact with a Sample System (SS) present on a Sample Systemsupporting Stage (STG). FIG. 1a 3 shows that said interaction with theSurface (S) of said Sample System (SS) causes a generally verticallyoriented Polarized Beam of Electromagnetic Radiation (LBO′) to passthrough Focusing Optic (F2). FIG. 1a 3 show that after passing throughFocusing Optic (F2) said generally vertically oriented Polarized Beam ofElectromagnetic Radiation (LBO′) interacts with Optical Element, (eg.Prism), (PRO) and is essentially totally internally reflected thereby tobecome generally horizontally oriented Polarized Beam of ElectromagneticRadiation (LBO), which generally horizontally oriented Polarized Beam ofElectromagnetic Radiation (LBO) passes through Analyzer (A) and thenenters Detector System (DET), via Circular Aperture (AP), for analysis.It is noted that the purpose of the Focusing Optics (F1) is to produce avery Concentrated High Intensity Small Area Polarized Beam ofElectromagnetic Radiation (LBI′) from Collimated Polarized Beam ofElectromagnetic Radiation (LBI). The purpose of Focusing Optic (F2) isto “Re-Collimate” the generally vertically oriented Polarized Beam ofElectromagnetic Radiation (LBO′) which results from the FocusedPolarized Beam of Electromagnetic Radiation (LBI′) being Reflected fromsaid Sample System (SS). The Re-Collimated generally vertically orientedBeam of Electromagnetic Radiation (LBI′) being identified as generallyhorizontally oriented Beam of Electromagnetic Radiation (LBO) after ithas been caused to interact with Prism (PRO).

Also, as in the FIG. 1a 2 case, note that after the Polarizer (P) thereis indicated, in dashed lines, the presence of a present inventionSpatial Filter (SF). Shown are a Pin Hole (PH), (which electromagneticbeam (LB1) passes through), which Pin Hole (PH) is located in a Diaphramwhich is located at essentially a Focal Length distant from each ofLenses (SFL1) and (SFL2). Again, while other pre-sample system locationsare included in the scope of the invention, the shown location ispreferred. Note that either of said Lenses (SFL1) and (SFL2) can bereplaced with a functionally essentially equivalent mirror.

FIG. 1a 4 shows a Spectroscopic Reflectance Mode version of the RotatingCompensator Ellipsometer System shown in FIG. 1a 1, with the DetectorElements (DE's) containing Photo Array Detector System (DET) shownpresent directly after the Analyzer (A).

FIG. 1a 5 shows another present invention system Reflectance ModeRotating Compensator Ellipsometer System System configuration in whichthree (3) Detectors (Det 1), (Det 2) and (Det 3) are fed input by FiberOptics (LF1), (LF2) and (LF3) present in a Fiber Optic Bundle exitingFiber Optic Connector (LFC). Said Fiber Optic Connector (LFC) receives aPolarized Electromagnetic Beam (EPCLB) exiting the Analyzer (A). Saidthree (3) Detectors (Det 1), (Det 2) and (Det 3) can be previouslydisclosed Off-the-shelf Zeiss Diode Array Spectrometers, and can eachcomprise a Focusing Element (FE) in functional combination with aDispersive Optics (DO) and a Diode Element (DE) containing Photo Array(PA). (Zeiss Diode Array Spectrometers provide, for instance,operational wavelength ranges selected from the group consisting of:(300-1150 nm, 190-230 nm, 190-400 nm and 900-2400 nm). It is alsomentioned that diffraction grating (DO) can be selected from the groupconsisting of: (a “lined”, a “blazed”, and a “holographic” geometry),said lined geometry consisting essentially of symetrical alternatinglines with depressions therebetween, and said blazed geometry consistingof alternating ramp shaped lines with depressions therebetween, and saidholographic geometry consisting of continuous cosine shaped lines anddepressions), all of which are known in the literature.

Both FIGS. 1a 4 and 1 a 5 show, in dashed lines, that at least oneSpatial Filter (SF) is present at at least one location somewhere in thedemonstrate Rotating Compensator Ellipsometer System. It is emphasisedthat said at least one Spatial Filter (SF) can be placed anywhere in thepresent invention Spectroscopic Rotating Compensator EllipsometerSystem, including just prior to the Detector (DET).

It is also noted that Fiber Optics can be utilized to carryPolychromatic Electromagnetic Radiation from a Source thereof (LS) tothe position of a Polarizer (P), or from the position of an Analyzer (A)to a Detector (DET) in FIGS. 1a 1-1 a 4, (see for instance (LF1), (LF2),and (LF3)).

Analogically similar figures to those shown in FIGS. 1a 3-1 a 5, butoriented for use in a Transmission Mode are not shown, but should beunderstood as within the scope of the present invention as implied by

FIG. 1a 1.

FIG. 2 shows that a Light Source (LS) can comprise a Light Fiber, a Lens(L1), and a First Aperture (A1). In the context of an ellipsometer aPolarizer (P) is also shown as it would be positioned. Shown in additionis a second Aperture (A2). In use electromagnetic radiation (EM) exitingthe Light Fiber (LF) expands and enters Lens (L1) and is collimatedthereby. First Aperture (A1) limits the beam diameter, and SecondAperture (A2) further does so to provide a beam of electromagneticradiation labeled (LB).

FIG. 3a expands on FIG. 2 and shows a present invention spatial filterconfiguration. The Spatial Filter (SF) is placed so as to intercept thebeam of electromagnetic radiation labeled (LB), and is converged by Lensor mirror (SFL1) such that it passes through a pin hole (PH), (thediameter of which is typically about half that of the Light Fiber (LF)and corresponds to the Image diameter of the Light Fiber (LF) at thelocation of said Pin Hole (PH)), and then is re-collimated by Lens ormirror (SFL2). Note that The Pin Hole diameter, however, is not criticaland can be bigger, and definitely smaller than just indicated, and canbe variable. Also, the Pin Hole (PH) is typically located a Focal Lengthdistant from each of the Lenses or mirrors (SFL1) and (SFL2). Again itis to be understood that either of the Lenses or mirrors (SFL1) and(SFL2) can be replaced by an essentially functionally equivalent mirror.

FIG. 3a also shows, (contained within dashed lines), that a FocusingLens (FL) can also be present, and when present is functionally muchlike the Lens labeled (F1) in FIG. 1a 3.

FIG. 3b shows alternative present invention Spatial Filter (SF)construction in which mirrors (SFM1) and (SFM2) perform the function oflenses (SFL1) and (SFL2) in FIG. 3a. That is the Spatial Filter shown inFIG. 3a can be replaced with that in FIG. 3b and remain within the scopeof the present invention. It is further noted that a present inventionSpatial Filter could comprise one Lens and one Mirror, in either orderin a Spatial Filter, hence the language “lens or mirror” is to beinterpreted broadly as meaning that each is independently selected fromthe group consisting of a lens and a mirror.

FIG. 4 shows the effect of the presence of the Spatial Filter (SF) asshown in FIG. 3a on the Intensity Profile of a beam of electromagneticradiation passed therethrough. Note that FIG. 4 plots Intensity on a LogAxis, and that the Intensity drops toward 0.001 much quicker when theSpatial Filter is in place than when it is not in place.

The present invention also includes, in the context of a spectroscopicellipsometer and the like systems, the method of removing an radialouter annular ring from an electromagnetic beam by use of a spatialfilter. Said method can be recited as a method of processing sourceelectromagnetic radiation beams to eliminate a radially outer annulusthereof, said outer annulus being comprised of low intensity levelirregular content, said method comprising placing at least one spatialfilter(s) such that said electromagnetic beam passes therethrough.

The terminology “outer annular region” as used herein is to beinterpreted to mean an outer region of an electromagnetic beam, asdistinct from a central region thereof, which outer region appears as anannulus when it is considered that the intensity of the beam decreasesto zero as the radius increases to infinity. Said “outer annulus region”at times begins at the point where the intensity of an electromagneticbeam falls to approximately ten (10%) percent of its maximum intensity,and it is noted, might contain approximately two (2%) to five (5%) ofthe electromagnetic beam's energy content.

It is also noted that a present invention Compensator (C) (C′), (C″) istypically an Off-the-Shelf Quarter-Wave-Plate with its Optical Axis inthe plane of a surface thereof, or Berek-type with its Optical Axisperpendicular to a surface thereof, and is selected without specialconcern to its Achromatic Operating Characteristics, emphasis added.Note that a Zero-Order Waveplate can be constructed from two (2)Multiple-Order Waveplates of different thicknesses (T1) and (T2) whichhave Optical Axes oreinted Ninety (90) degrees to one another, such thatthe overall effect of retardation in in the Zero-Order. As well, saidCompensator (C), (C′), (C″) can be made of essentially any functionalmaterial such as Quartz or Polymer etc.

Now, and importantly, even though the Present Invention RotatingRotating Ellipsometer System is Spectroscopic, (ie. simultaneouslyoperates on a number of Wavelengths in a Beam containing manyElectromagnetic Wavelengths, over a range of, for instance, 190-1000nanometers), a Compensator (C), (C′), (C″) utilized therein can providea Retardance which, for instance, varies inversely with Wavelength andstill be usable. A Compensator (C), (C′), (C″) does however, typically,have to be of a nature to allow passage of a PolychromaticElectromagnetic Beam therethrough without causing significantAttenuation, Deviation or Displacement in the Direction of Propagationthereof. If this is not the case, difficult to compensate complexitiesare caused in Detector Elements (DE's) containing Photo Array DetectorSystem (DET) Detector Element Output Signals.

The reason the Present Invention can operate with a Compensator (C),(C′), (C″) that does not provide even close to a Constant Ninety (90)Degree Retardance over a range of Wavelengths, (which would constituteIdeal Characteristics), is that a Regression based Calibration Procedureutilized, (see U.S. Pat. No. 5,872,630 which is incorporated byreference hereinto, and which is co-owned with this Application),provides Wavelength dependent Compensation effecting values forCalibration Parameters as required in a developed Mathematical Model ofthe present invention Rotating Compensator Ellipsometer System. Asbetter described in the 630 Patent the Inventors develop a CalibrationParameter Containing Mathematical Model of the present inventionRotating Compensator Ellipsometer System by, for instance, utilizingMatrix Representations for various System Components involved, thenmultiplies out the Matrices in an appropriate order to provide aTransfer Function. This applies for all Wavelengths monitored by aDetector Elements (DE's) containing Photo Array Detector System (DET)Detector Element (DE). Next, Data Set(s) are Experimentally obtained asa function of wavelength and typically as a function of various settingsof the Polarizer (P) or Analyzer (A), (or both could be rotated tovarious positions), while a Compensator (C) rotates at, typically thoughnot necessarily, Twenty (20) to Thirty (30) Hz. Other rotation speedscan be utilized and if two Compensators are present one or both can becaused to rotate, and if both are caused to rotate, as mentioned earlierherein, they can be caused to rotate at the same, or different, speeds.(Note that Data Set(s) could also be achieved utilizing variation ofAngle-Of-Incidence of a Beam of Polychromatic Radiation with respect toa Sample System under investigation). Calibration Parameters in theMathematical Model are then evaluated by, typically, Mean-Square-Errorbased Regression onto the Data Set(s). It is also possible toeffectively find Calibration Parameter containing MathematicalExpressions for Coefficients of Mathematical Series, (eg. FourierSeries), which comprise the Mathematical Model Transfer Function, andcalculate Numerical Values for the Coefficients from the Data Set(s),then effectively perform Regression of said Calibration Parametercontaining Mathematical Expressions for Coefficients of MathematicalSeries Transfer Function onto said Numerical Values for the Coefficientsfrom the Data Set(s). It is emphasized that a single Two-DimensionalData Set has been found sufficient to allow excellent Calibrationresults to be achieved. Said Two-Dimensional Data Set typically isIntensity vs. Wavelength, and Polarizer or Analyzer Azimuthal RotationAngle settings. In addition, said Two-Dimensional Data Set can beobtained from a present invention Rotating Compensator EllipsometerSystem oriented so that a Polychromatic Beam of ElectromagneticRadiation interacts with a Sample System or such that said PolychromaticBeam of Electromagnetic Radiation passes through the present inventionRotating Compensator Sample System Investigation System withoutinteracting with a Sample System, other than a Sample System comprisedof “Open Atmosphere”. The present invention Rotating RotatingEllipsometer System can also, of course, be Calibrated utilizing morethan one Data Set as well, but as alluded to, this has not been foundnecessary. This is mentioned as the invention reported in Co-pendingpatent application Ser. No. 08/618,820, wherein a Rotating RotatingEllipsometer System utilized in the Infra-red band of wavelengths,requires that two (2) Data Sets be present, (eg. selected with theRotating Compensator Sample System Investigation System oriented in amanner selected from the group: (“Straight-Through”, “Sample SamplePresent”, “Alternative Sample Sample Present”)). Both Data Sets aresimultaneously utilized in a Regression Procedure to evaluate numerousCalibration Coefficients in a Mathematical Model which is described inthe Ser. No. 08/618,820 Application. The reason that only one (1) DataSet is required to practice the described present invention CalibrationProcedure, is that the number of Calibration Parameters required by theMathematical Model of the present invention, (which is not operated inthe Infra-red range of wavelengths), is much fewer that the number ofCalibration Parameters required by the Mathematical Model of theRotating Rotating Ellipsometer System operated in the Infra-red range ofwavelengths. The present invention Rotating Compensator SystemMathematical Model typically involves as few as Five (5) CalibrationParameters, (where only one Compensator is present), in combination withsimultaneous determination of a Sample System PSI and DELTA. (It isnoted that a straight-through mode essentially provides open atmosphereas a Sample System and that the PSI and DELTA of open atmosphere areforty-five (45) degrees and zero (0.0) degrees, respectively). Said Five(5) Calibration Parameters are Azimuthal Orientation Angles forPolarizer (Ps), Analyzer (As), Compensator (Cs), and CompensatorRetardance Parameters (P0) and (P1). Equations (45) and (46) serve asfurther demonstratration of this point. (Note that the (Ps), (Cs) and(As) Azimuthal Orientation Calibration Angles can be thought of asserving to align the Polarizer, Compensator and Analyzer Azimuths with aSample System Frame of Reference). Of course, if two Compensators arepresent then an additional Compensator Orientation Angle (Cs2) andCompensator Retardance Parameters (P0′) and (P1′) and additional wouldalso have to be evaluated. (It is noted that Retardation entered betweenorthogonal components of a Polarized Electromagnetic Beam, by aCompensator, is accounted for by a Matrix Component, and typically ther4 term of a Jones Matrix, but such is accounted for by CompensatorRetardation Parameters (P0), (P1), (P0′), (P1′) in the presentlydescribed Calibration Procedure).

Continuing, the present invention achieves a Spectroscopic RotatingRotating Ellipsometer System preferably utilizing an “Off-The-Shelf”compact Spectrometer Systems, and utilizing “Off-The-Shelf” CompensatorComponents which are not at all “ideal”, as regards Achromaticity. Toput this into perspective, it is noted that to date, there is no knownSpectroscopic Rotating Compensator Ellipsometer available in themarket-place. It is believed that this is because it has previously beenbelieved that to achieve such a System an Achromatic RotatingCompensator (RC) would be required. Such Compensators are not generallycommercially available, hence, are expensive and reasonableapproximations thereof typically must be individually fabricated. (Note,as described in patent application Ser. No. 08/618,820, (now U.S. Pat.No. 5,706,212), a Dual-Rhomb Rotating Compensator (RC) which providesabout seven (7%) percent variation in Retardation effected over a rangeof Wavelengths of approximately 2 to 14 microns, has been developed atthe University of Nebraska. However, it is not clear that even theidentified University of Nebraska Dual-Rohmb Rotating Compensator (RC)would operate “Achromatically” outside the identified range ofwavelengths).

Further, essentially any Compensator which can be placed into a beam ofelectromagnetic radiation can be applied, such as those disclosed inclaim 9 of U.S. Pat. No. 5,872,630, (which 630 Patent is incorporated byreference hereinto):

Berek-type;

Non-Berek-type;

Zero Order;

Zero Order comprising a plurality of plates;

Rhomb;

Polymer;

Achromatic Crystal; and

Psuedo-Achromatic.

FIGS. 5a, 5 b, 5 c, 5 d and 5 e demonstrate functional construction ofpreferred present invention compensator systems. FIG. 5a simplyexemplifies that a single plate (SPC) compensator (1) can be applied.FIG. 5b demonstrates construction of a compensator (2) from first (ZO1)and second (ZO2) effectively Zero-Order, (eg. Quartz or BicrystalineCadnium Sulfide or Bicrystaline Cadnium Selenide), Waveplates, each ofwhich effective Zero-Order Waveplates (ZO1) & (ZO2) is shown to beconstructed from two Multiple Order waveplates, (ie. (MOA1) & (MOB1) and(MOA2) & (MOB2), respectively). The fast axes (FAA2) & (FAB2) of saidsecond effective Zero-Order Waveplate (ZO2) are oriented away from zeroor ninety degrees, (eg. in a range around a nominal forty-five degreessuch as between forty and fifty degrees), with respect to the fast axes(FAA1) & (FAB1) of said first effective Zero-Order Waveplate (ZO1). Inparticular FIG. 5b is a cross-sectional side view of a present inventionpreferred compensator (PC) constructed from a first effective zero-orderplate (ZO1) which is constructed from two multiple order plates (MOA1)and (MOB1), and a second effective zero-order plate (ZO2) which isconstructed from two multiple order plates (MOA2) and (MOB2). An enteredelectromagnetic beam (EMBI) emerges as electromagnetic beam (EMBO) witha retardation entered between orthogonal components thereof with aRetardation vs. Wavelength. FIGS. 5c and 5 d are views looking into theleft and right ends of the preferred present invention Compensator (PC)as shown in FIG. 5b, and show that the Fast Axes (FAA2) and (FAB2) ofthe second effective Zero-Order Waveplate (ZO2) are rotated away fromzero or ninety degrees and are ideally oriented at forty-five degrees,with respect to the Past Axes (FAA1) & (FAB1) of the first effectiveZero-Order Waveplate (ZO1). (Note that the fast axis (FAA1) of the firsteffective Zero-Order Waveplate (ZO1) is shown as a dashed line in FIG.5d, for reference). FIG. 5e demonstrates functional construction ofanother preferred compensator (2′) which is constructed from two per se.single plate Zero-Order Waveplates (MOA) and (MOB), which are typicallymade of materials such as mica or polymer.

(It is specifically to be understood that a present inventioncompensator system can be comprised of at least one Zero-Order waveplateand at least one effectively Zero-Order waveplate in combination, aswell as combinations comprised of two actual Zero-Order waveplates ortwo effectively Zero-Order waveplates).

FIGS. 5f-5 m demonstrate additional compensators which can be applied inthe present invention.

FIG. 5f shows that the first additional present invention retardersystem (3) comprises a first triangular shaped element (P1), which asviewed in side elevation presents with first (OS1) and second (OS2)sides which project to the left and right and downward from an upperpoint (UP1). Said first triangular shaped element (P1) first (OS1) andsecond (OS2) sides have reflective outer surfaces. Said retarder system(3) further comprises a second triangular shaped element (P2) which asviewed in side elevation presents with first (IS1) and second (IS2)sides which project to the left and right and downward from an upperpoint (UP2), said second triangular shaped element (P2) being made ofmaterial which provides internally reflective, phase delay introducing,interfaces on first (IS1) and second (IS2) sides inside thereof. Saidsecond triangular shaped element (P2) is oriented with respect to thefirst triangular shaped element (P1) such that the upper point (UP2) ofsaid second triangular shaped element (P2) is oriented essentiallyvertically directly above the upper point (UP1) of said first triangularshaped element (P1). In use an input electromagnetic beam of radiation(LB) caused to approach said first (OS1) side of said first triangularshaped element (P1) along an essentially horizontally oriented locus, isshown as being caused to externally reflect from an outer surfacethereof and travel along as electromagnetic beam of radiation (R1) whichis essentially upwardly vertically oriented. Next said electromagneticbeam of radiation (R1) is caused to enter said second triangular shapedelement (P2) and essentially totally internally reflect from said first(IS1) side thereof, then proceed along an essentially horizontal locusand essentially totally internally reflect from the second (IS2) sidethereof and proceed along an essentially downward vertically orientedelectromagnetic beam of radiation (R3). This is followed by an externalreflection from an outer surface of said second side (OS2) of said firsttriangular shaped element (P1) such that said electromagnetic beam (LB′)of radiation proceeds along an essentially horizontally oriented locus,undeviated and undisplaced from the essentially horizontally orientedlocus of said input beam (LB) of essentially horizontally orientedelectromagnetic radiation. This is the case even when said retardersystem (3) is caused to rotate. The result of said described retardersystem (3) application being that retardation is entered betweenorthogonal components of said input electromagnetic beam of radiation(LB). Further, said first (P1) and second (P2) triangular shapedelements are typically right triangles in side elevation as shown inFIG. 5f, and the outer surfaces of first (OS1) and second (OS2) sidesare typically, but not necessarily, made reflective by the presence of acoating of metal thereupon. A coating of metal serves assure a highreflectance and good electromagnetic beam radiation intensitythroughput. Also, assuming accurately manufactured right angle first(P1) and second (P2) triangular shaped elements are utilized, thiscompensator design provides inherent compensation of both angular andtranslational misalignments of the input light beam (LB). As well, thetotal retardence provided is compensated for angular misalignments ofthe input electromagnetic radiation beam. That is, if the inputelectromagnetic radiation beam (LB) is not aligned so as to form anangle of incidence of forty-five (45) degrees with the first outersurface (OS1), the reflected electromagnetic beam (R1) will internallyreflect at the first internal surface (IS1) of the second triangularshaped element (P2) at a larger (smaller) angle than would be the caseif said angle of incidence were forty-five (45) degrees. This effect,however, is directly compensated by a smaller (larger) angle ofincidence of electromagnetic beam (R2) where it internally reflects frominner surface (IS2) of the second triangular shaped element (P2). Asanother comment it is to be understood that because of the obliqueangles of incidence of the reflections from the outer surfaces (OS1) and(OS2) of the first triangular shaped element (P1) apolarimeter/ellipsometer in which said compensator (3) is present willrequire calibration to characterize the PSI-like component thereof.

FIG. 5g shows a variation (3′) on FIG. 5f, wherein the first triangularshaped element is replaced by two rotatable reflecting means, identifiedas (OS1′) and (OS2′). This modification allows user adjustment so thatthe locus of an entering electromagnetic beam (LB′) exits undeviated andundisplaced from an entering electromagnetic beam (LB).

FIG. 5h shows that the second additional present invention retardersystem (4) comprises a parallelogram shaped element which, as viewed inside elevation, has top (TS) and bottom sides (BS), each of length (d)parallel to one another, both said top (TS) and bottom (NS) sides beingoriented essentially horizontally. Said retarder system (4) also hasright (RS) and left (LS) sides parallel to one another, both said right(RS) 5 and left (LS) sides being of length (d/cos(∝)), where alpha (∝)is shown as an angle at which said right (RS) and left (LS) sidesproject from horizontal. Said retarder system (4) is made of a materialwith an index of refraction greater than that of a surrounding ambient.In use an input beam of electromagnetic radiation (LB) caused to enterthe left side (LS) of said retarder system (4), along an essentiallyhorizontally oriented locus, is caused to diffracted inside saidretarder system (4) and follow a locus which causes it to essentiallytotally internally reflect from internal interfaces of both said top(TS) and bottom (BS) sides, and emerge from said retarder system (4) as(LB′) from the right side (RS) thereof, along an essentiallyhorizontally oriented locus which is undeviated and undisplaced from theessentially horizontally oriented locus of said input beam (LB) ofessentially horizontally oriented electromagnetic radiation. This is thecase even when said retarder system (4) is caused to rotate. The resultof said described retarder system (4) application being that retardationis entered between orthogonal components of said input electromagneticbeam of radiation at said internal reflections from the top (TS) andbottom (BS) surfaces. This retarder system is very robust as it is madeof single piece construction. It is noted that adjustment of the anglealpha (∝) in manufacture allows setting the amount of retardation whichis provided by the retarder system (4). In addition, coatings can beexternally applied to top (TS) and bottom surface (BS) to adjustretardation effected by internal reflection from said top (TS) andbottom (BS) surfaces. A formula which defines the retardation providedthereby being:

FIG. 5i shows that the third additional present invention retardersystem (5) comprises first (P1) and second (P2) triangular shapedelements. Said first (P1) triangular shaped element, as viewed in sideelevation, presents with first (LS1) and second (RS1) sides whichproject to the left and right and downward from an upper point (UP1),said first triangular shaped element (P1) further comprising a thirdside (H1) which is oriented essentially horizontally and which iscontinuous with, and present below said first (LS1) and second (RS1)sides. Said second triangular shaped element (P2), as viewed in sideelevation, presents with first (LS2) and second (RS2) sides whichproject to the left and right and upward from a lower point (LP2), saidsecond triangular shaped element (P2) further comprising a third side(H2) which is oriented essentially horizontally and which is continuouswith, and present above said first (LS2) and second (RS2) sides. Saidfirst (P1) and second (P2) triangular shaped elements being positionedso that a rightmost side (RS1) of said first (P1) triangular shapedelement is in contact with a leftmost side (LS2) of said second (P2)triangular shaped element over at least a portion of the lengthsthereof. Said first (P1) and second (P2) triangular shaped elements areeach made of material with an index of refraction greater than that of asurrounding ambient. In use an input beam (LB) of electromagneticradiation caused to enter the left (LS1) side of said first (P1)triangular shaped element and is caused to diffracted inside saidretarder system (5) and follow a locus which causes it to essentiallytotally internally reflect from internal interfaces of said third sides(H1) and (H) of said first (P1) and second (P2) triangular shapedelements, respectively, and emerge from said right side (RS2) of saidsecond (P2) triangular shaped element as electromagnetic radiation beam(LB′) which is oriented along an essentially horizontal locus which isundeviated and undisplaced from the essentially horizontally orientedlocus of said input beam (LB) of essentially horizontally orientedelectromagnetic radiation. This is the case even when said retardersystem (5) is caused to rotate. The result of said described retardersystem (5) application being that retardation is entered betweenorthogonal components of said input electromagnetic beam of radiation(LB). It is noted that as long as the third sides (H1) and (H2) of saidfirst (P1) and second (P2) triangular shaped elements are parallel, theoutput electromagnetic beam (LB′) is undeviated and undisplaced from theinput electromagnetic beam (LB) in use. It is noted that the triangularshape elements (P1) and/or (P2) can be made of various materials withvarious indicies of refraction, and coating(s) can be applied to one orboth of the third sides (H1) and (H2) of said first (P1) and second (P2)triangular shaped elements to adjust retardation entered to anelectromagnetic beam (LB1).

FIG. 5j shows that the fourth additional present invention retardersystem (6) comprises a triangular shaped element, which as viewed inside elevation presents with first (LS) and second (RS) sides whichproject to the left and right and downward from an upper point (UP).Said retarder system (6) further comprises a third side (H) which isoriented essentially horizontally and which is continuous with, andpresent below said first (LS) and second (RS) sides. Said retardersystem (6) is made of a material with an index of refraction greaterthan that of a surrounding ambient. In use an input beam ofelectromagnetic radiation (LB) caused to enter the first (LS) side ofsaid retarder system (6) along an essentially horizontally orientedlocus, is caused to diffracted inside said retarder system (6) andfollow a locus which causes it to essentially totally internally reflectfrom internal interface of said third (H) side, and emerge from saidretarder system (6) from the second (RS) side along an essentiallyhorizontally oriented locus which is undeviated and undisplaced from theessentially horizontally oriented locus of said input beam ofessentially horizontally oriented electromagnetic radiation (LB). Thisis the case even when said retarder system (6) is caused to rotate. Theresult of said described retarder system (6) application being thatretardation is entered between orthogonal components of said inputelectromagnetic beam of radiation (LB). The FIG. 5j retarder system (6)is typically an isosceles prism which is available off-the-shelf with anangle alpha (∝) of forty-five (45) degrees. As long as the inputelectromagnetic beam (LB) height (h) is chosen in accordance with theformula:${d = {2{h\left( {\frac{1}{\tan (\alpha)} + {\tan (\varphi)}} \right)}}},{{{where}\quad \varphi} = {\alpha + {\sin^{- 1}\left( \frac{\sin \left( {90 - \alpha} \right)}{n} \right)}}}$

in conjunction with the index of refraction (n) of the material fromwhich the FIG. 5j retarder system (6) is made, and the locus of theinput electromagnetic radiation beam (LB) is parallel with the thirdside (H) of said retarder system (6), the output electromagnetic beam(LB′) will not be deviated or translated with respect to the inputelectromagnetic beam (LB). As well, note the dashed line (DL) below theupper point (UP). This indicates that as the region above said dashedline (DL) is not utilized, the portion of said retarder system (6)thereabove can be removed. It is also noted that the inputelectromagnetic beam (LB) enters and exits the retarder system (6) otherthan along a normal to a surface thereof, said retarder system is not anideal retarder with a PSI of forty-five (45) degrees. It is noted thatthe third side (H) of the retarder system (6) can be coated to changethe retardation effects of an internal reflection of an electromagneticbeam of radiation therefrom, and such a coating can have an adverseeffect on the nonideal PSI characteristics.

FIG. 5m shows that the fifth additional present invention retardersystem (7) comprises first (PA1) and second (PA2) parallelogram shapedelements which, as viewed in side elevation, each have top (TS1)/(TS2)and bottom (BS1)/(BS2) sides parallel to one another, both said top(TS1) (TS2) and bottom (BS1) (BS2) sides each being oriented at an angleto horizontal. Said first (PA1) and second (PA2) parallelogram shapedelements also each have right (RS1)/(RS2) and left (LS1)/(LS2) sidesparallel to one another, all said right (RS1) (RS2) and left (LS1) (LS2)sides being oriented essentially vertically. Said first (PA1) and second(PA2) parallelogram shaped elements are made of material with an indexof refraction greater than that of a surrounding ambient. A right mostvertically oriented side (RS1) of said first parallelogram is in contactwith a leftmost (LS2) vertically oriented side of the secondparallelogram shaped element (PA2). In use an input beam ofelectromagnetic radiation (LB) caused to enter an essentially verticallyoriented left side (LS1) of said first parallelogram shaped element(PA1) along an essentially horizontally oriented locus, is caused to bediffracted inside said retarder system and follow a locus which causesit to essentially totally internally reflect from internal interfaces ofboth said top (TS1) (TS2) and bottom (BS1) (BS2) sides of both saidfirst and second parallelogram shaped elements (PA1) (PA2), then emergefrom a right side (RS2) of said second parallelogram shaped element(PA2) along an essentially horizontally oriented locus as output beam ofelectromagnetic radiation (LB′) which is undeviated and undisplaced fromthe essentially horizontally oriented locus of said input beam ofessentially horizontally oriented electromagnetic radiation (LB). Thisis the case even when said retarder system (7) is caused to rotate. Theresult of said described retarder system (7) application being thatretardation is entered between orthogonal components of said inputelectromagnetic beam of radiation (LB).

FIG. 5k 1 shows that the sixth additional present invention retardersystem (8) comprises first (BK1) and second (BK2) Berek-type retarderswhich each have an optical axes essentially perpendicular to a surfacethereof. As shown by FIG. 5k 2, each of said first (BK1) and second(BK2) Berek-type retarders can have fast axis which are oriented otherthan parallel to one another, but for the presently described retardersystem it is assumed that the fast axes are aligned, (ie. an angle PHI(φ) of zero (0.0) degrees exists between fast axes of the two Berek-type(BK1) and (BK2) plates in FIG. 5k 1. Said first and second Berek-typeretarders each present with first and second essentially parallel sides.Said first (BK1) and second (BK2) Berek-type retarders are oriented, asviewed in side elevation, with first (LS1) and second (RS1) sides of oneBerek-type retarder (BK1) being oriented other than parallel to first(LS2) and second (RS2) sides of the other Berek-type retarder (BK2). Inuse an incident beam of electromagnetic radiation (LB) is caused toimpinge upon one of said first (BK1) Berek-type retarder on one side(LS1) thereof, partially transmit therethrough then impinge upon thesecond Berek-type retarder (BK2), on one side thereof (LS2), andpartially transmit therethrough such that a polarized beam ofelectromagnetic radiation (LB′) passing through both of said first (BK1)and second (BK2) Berek-type retarders emerges from the second thereof ina polarized state with a phase angle between orthogonal componentstherein which is different than that in the incident beam ofelectromagnetic radiation (LB), and in a direction which is anessentially undeviated and undisplaced from the incident beam ofelectromagnetic radiation. This is the case even when said retardersystem (8) is caused to rotate. The result of said described retardersystem (8) application being that retardation is entered betweenorthogonal components of said input electromagnetic beam of radiation.For insight it is mentioned that, in general, a Berek-type retarder is auniaxial anisotropic plate with its optical axis essentiallyperpendicular to a surface thereof. The retardence introduced to anelectromagnetic beam caused to transmit therethrough is determined by atipping of said plate. The retardation system (8) having two suchBerek-type retarders present, is, it is noted, insensitive to smallangular deviations in an input electromagnetic beam as each platecontributes approximately half of achieved retardence. Thisinsensitivity results because if the input electromagnetic beam isslightly changed, one of said plates will contribute slightly more(less), but the second slightly less (more) retardence because ofoffsetting effective plate “tilts” with respect to electromagnetic beamsinput thereto. Also, said retarder system (8) is very nearly ideal inthat the PSI component of the retarder system (8) is very near aconstant forty-five (45) degrees. One problem however, is thatBerek-type retarder plates exhibit a (1/wavelength) retardencecharacteristic which, without more, makes use over a wide spectral rangedifficult.

A variation of the just described retarder system (8) applies to theseventh additional present invention retarder system (9) as well, withthe difference being that a FIG. 5k 2 offset angle PHI (φ) other thanzero (0.0) is present between fast axes of the two Berek-type plates.The description of the system remains otherwise unchanged. The benefitderived, however, is that a flatter than (1/wavelength) retardationcharacteristic can be achieved thereby.

FIG. 5l 1 serves as the pictorial reference for the eighth additionalpresent invention retarder system (8) which comprises first (BK1),second (BK2), third (BK3) and fourth (BK4) Berek-type retarders whicheach have an optical axes essentially perpendicular to a surfacethereof, each of which first (BK1) and second (BK2) Berek-type retardershas a fast axis, said fast axes in said first (BK1) and second (BK2)Berek-type retarders being oriented essentially parallel to one another.This is exemplified by FIG. 5l 2. Said first (BK1) Berek-type retarderpresents with first (LS1) and second (RS1) essentially parallel sidesand said second (BK2) Berek-type retarders each present with first (LS2)and second (RS2) essentially parallel sides, and said first (BK1) andsecond (BK2) Berek-type retarders are oriented, as viewed in sideelevation, with first (LS1) and second (RS1) sides of said firstBerek-type retarder being oriented other than parallel to first (LS2)and second (RS2) sides of said second (BK2) Berek-type retarder. In usean incident beam of electromagnetic radiation (LB) is caused to impingeupon said first (BK1) Berek-type retarder on said first side (LS1)thereof, partially transmit therethrough then impinge upon the second(BK2) Berek-type retarder, on said first (LS2) side thereof, andpartially transmit therethrough such that a polarized beam ofelectromagnetic radiation (LB′) passing through both of said first (BK1)and second (BK2) Berek-type retarders emerges from the second thereof ina polarized state with a phase angle between orthogonal componentstherein which is different than that in the incident beam ofelectromagnetic radiation (LB), and in a direction which is anessentially undeviated and undisplaced from the incident beam ofelectromagnetic radiation (LB). Each of which third (BK3) and fourth(BK4) Berek-type retarders also has a fast axis, and said fast axes insaid third (BK3) and fourth (BK4) Berek-type retarders are orientedessentially parallel to one another but other than parallel to theparallel fast axes of said first (BK1) and second (BK2) Berek-typeretarders. Said third (BK3) Berek-type retarder presents with first(LS3) and second (RS3) essentially parallel sides, and said fourth (BK4)Berek-type presents with first (LS4) and second (RS4) essentiallyparallel sides, and said first third (BK3) and fourth (BK4) Berek-typeretarders are oriented, as viewed in side elevation, with first (LS3)and second (RS3) sides of one of said third (BK3) Berek-type retarderbeing oriented other than parallel to first (LS4) and second (RS4) sidesof said fourth (BK4) Berek-type retarder; such that in use an incidentbeam of electromagnetic radiation (LB′) exiting said second (BK2)Berek-type retarder is caused to impinge upon said third (BK3)Berek-type retarder on said first (LS3) side thereof, partially transmittherethrough then impinge upon said fourth (BK4) Berek-type retarder onsaid first (LS4) side thereof, and partially transmit therethrough suchthat a polarized beam of electromagnetic radiation (LB″) passing throughsaid first (BK1), second (BK2), third (BK3) and fourth (BK4) Berek-typeretarders emerges from the fourth (BK4) thereof in a polarized statewith a phase angle between orthogonal components therein which isdifferent than that in the incident beam of electromagnetic radiation(LB) caused to impinge upon the first (LS1) side of said first (BK1)Berek-type retarder, in a direction which is an essentially undeviatedand undisplaced from said incident beam of electromagnetic radiation(LB). This is the case even when said retarder system (8) is caused torotate. The result of said described retarder system (8) applicationbeing that retardation is entered between orthogonal components of saidinput electromagnetic beam of radiation.

A ninth present invention retarder system (9) is also pictoriallyrepresented by FIG. 5l 1 and is similar to that just described exceptingthat the Berek-type retarder plates (BK1) and (BK2) fast axes need notbe parallel to one another and the Berek-type retarder plates (BK3) and(BK4) need not be parallel to one another. However, if as a groupBerek-type retarder plates ((BK1) and (BK2))/((BK3) and (BK4)) areparallel, they can be, but need not be parallel the fast axes ofBerek-type retarder plates ((BK3) and (BK4))/((BK1) and (BK2)). Thisembodiment includes the case where all the fast axes of all Berek-typeretarders (BK1), (BK2), (BK3) and (BK4) are all different. FIG. 5l 2shows the relative angular orientations between pairs of Berek Plates.

It is also to be appreciated that no other Spectroscopic RotatingCompensator System is known which comprises at once:

1. at least one non-Achromatic Characteristic Rotating Compensator (RC);

2. a Dispersive Optics (DO);

3. a Detector Elements (DE's) containing Detector System (DET) whichcomprises a Photo Array (PA); such that in use a Multiplicity of SampleSystem (SS) Investigation Wavelengths in a Polychromatic Beam ofElectromagnetic Wavelengths are simultaneously Monitored; and

4. a Spatial Filter located at any location between Source (LS) andDetector (DET).

It is emphasized that the present invention is considered to beparticularly impressive as it is relatively easily constructed utilizingcommercially available “Off-The-Shelf” Diode Array Spectrometer Systems,and non-ideal Compensators. The present invention conveniently provides,in a commercially realizable format, that which was thought to be, priorto the present invention, essentially impossibly to provide in otherthan a prohibitively expensive, (and perhaps difficult to calibrate andutilize), single unit format.

It is to be understood tha ta Photo Array can be comprised ofDiode-Elements, Charge-Coupled-Devicies, Bucket-Brigade-Devices andequivalents.

It is noted that “deviation” refers to a change in the direction, anddisplacement refers to an offset in said direction of propagation ofpropagation of a beam of electromagnetic radiation, when it passesthrough an optical element.

It is also noted that Polychromatic Electromagnetic Beam Source can becomprised of a combined plurality/multiplicity of Laser Sources, andthat Polychromatic Electromagnetic Beam Source can include an effectivePolarizer therewithin, thereby eliminating the need for a separatePolarizer. Such cases are to be considered within the scope of theClaims.

It is also noted that the language “at least partially passthere-through” regarding an electromagnetic beam interaction with a pinhole in a diaphram, means that at least a part of said beam passesthrough the aperture, said part typically being centrally located insaid beam, with an annular region being blocked passage.

Finally, it is to be understood that a spatial filter basicallyseqentially consists of beam converging at least one lens and/or mirror,a diaphram with a pin hole therein located essentially at the focallength of said beam converging lens and/or mirror, and a second beamcollimating at least one lens and/or mirror. However, it should beappreciated that, for instance, a first beam collimating lens andaperture can be added and the resulting system still be within the scopeof a spatial filter.

Having hereby disclosed the subject matter of this invention, it shouldbe obvious that many modifications, substitutions and variations of thepresent invention are possible in light of the teachings. It istherefore to be understood that the present invention can be practicedother than as specifically described, and should be limited in breadthand scope only by the Claims.

We claim:
 1. A spectroscopic rotating compensator ellipsometer systemcomprising a source of a polychromatic beam of electromagneticradiation, a polarizer, a stage for supporting a sample system, ananalyzer, a dispersive optics and at least one detector system whichcontains a multiplicity of detector elements, said spectroscopicrotating compensator ellipsometer system further selected from the groupconsisting of: before said stage for supporting a sample system; andafter said stage for supporting a sample system; and both before andafter said stage for supporting a sample system; such that when saidspectroscopic rotating compensator ellipsometer system is used toinvestigate a sample system present on said stage for supporting asample system, said analyzer and polarizer are maintained essentiallyfixed in position and at least one of said at least one compensator(s)is caused to continuously rotate while a polychromatic beam ofelectromagnetic radiation produced by said source of a polychromaticbeam of electromagnetic radiation is caused to pass through saidpolarizer and said compensator(s), said polychromatic beam ofelectromagnetic radiation being also caused to interact with said samplesystem, pass through said analyzer and interact with said dispersiveoptics such that a multiplicity of essentially single wavelengths arecaused to simultaneously enter a corresponding multiplicity of detectorelements in said at least one detector system; the improvement beingthat said spectroscopic rotating compensator ellipsometer system furthercomprises, before and/or after a sample system: at least one spatialfilter which, for instance, serves to attenuate an outer annular regionfrom said electromagnetic beam as it passes therethrough.
 2. A system asin claim 1 in which said spatial filter sequentially comprises: firstbeam collimating lens; aperture; beam converging at least one lensand/or mirror; diaphram with a pin hole therein located essentially atthe focal length of said at least one beam converging lens and/ormirror; and second beam collimating at least one lens and/or mirror;such that in use the central portion of the electromagnetic beam whichis collimated by said first beam collimating lens is caused to passthrough said aperture, become focused on and at least partially passthrough said pin hole in said diaphram by said at least one beamconverging lens and/or mirror, and become recollimated by said secondbeam collimating at least one lens and/or mirror.
 3. A system as inclaim 1 wherein a source of electromagnetic radiation is in functionalcombination with said spatial filter which sequentially comprises: beamconverging at least one lens and/or mirror; diaphram with a pin holetherein located essentially at the focal length of said at least onebeam converging lens and/or mirror; and beam collimating at least onelens and/or mirror; such that in use an electromagnetic beam ofradiaiton is caused to become focused on and at least partialy passthrough said pin hole in said diaphram by said beam converging at leastone lens and/or mirror, and then become recollimated by said beamcollimating at least one lens and/or mirror.
 4. A system as in claim 1,in which the spectroscopic rotating compensator ellipsometer system ischaracterized as: a polarization state generator comprising said sourceof a polychromatic beam of electromagnetic radiation and said polarizerprior to said means for supporting a sample system; and a polarizationstate detector comprising said analyzer, a dispersive optics and atleast one detector system which contains a multiplicity of detectorelements, after said means for supporting a sample system; at least oneof said polarization state generator and polarization state detectorfurther comprising a compensator; a spatial filter being present in atleast one selection from the group consisting of: said polarizationstate generator; and said polarization state detector.
 5. A system as inclaim 4, in which said at least one spatial filter sequentiallycomprises: first at least one lens and/or mirror; pin hole containingdiaphram; and second at least one lens and/or mirror; said pin holecontaining diaphram being positioned near the focal points of said firstand second at least one lenses and/or mirrors, such that a collimatedelectromagnetic beam enters said first at least one lens and/or mirror,is converged and at least partially passes through said pin hole, and isre-collimated by said second at least one lens and/or mirror.
 6. Asystem as in claim 1, in which said at least one spatial filtersequentially comprises: first at least one lens and/or mirror; pin holecontaining diaphram; and second at least one lens and/or mirror; suchthat a collimated electromagnetic beam enters said first at least onelens and/or mirror, is converged and at least partially passes throughsaid pin hole, and is re-collimated by said second at least one lensand/or mirror.
 7. A spectroscopic rotating compensator ellipsometersystem as in claim 1 in which dispersive optics and detector elementsare contained in an off-the-shelf diode array spectrometer system.
 8. Aspectroscopic rotating compensator sample system investigation system asin claim 7 in which said off-the-shelf diode array spectrometer systemis manufactured by Zeiss and provides an operational wavelength rangeselected from the group consisting of: 300-1150 nm, 190-230 nm, 190-400nm and 900-2400 nm.
 9. A spectroscopic rotating compensator ellipsometersystem as in claim 1 in which the compensator(s) is/are non-achromaticin that retardation effected thereby between quadrature components of abeam of electromagnetic radiation at one wavelength is different thanthat provided thereby at at least one other wavelength.
 10. Aspectroscopic rotating compensator ellipsometer system as in claim 9 inwhich the non-achromatic compensator(s) presents with a retardance vs.wavelength characteristic essentially proportional to (1/wavelength).11. A spectroscopic rotating compensator sample ellipsometer system asin claim 1 in which the compensator(s) is/are achromatic in thatretardation effected thereby between quadrature components of a beam ofelectromagnetic radiation at one wavelength is essentially the same asthat provided thereby at other wavelengths.
 12. A spectroscopic rotatingcompensator ellipsometer system as in claim 1 in which said at least oneof said at least one compensator(s) causes essentially no deviation ordisplacement in a polychromatic beam of electromagnetic radiation causedto pass therethrough while caused to rotate.
 13. A spectroscopicrotating compensator ellipsometer system as in claim 1 in which said atleast one of said at least one compensator(s) is of a type selected fromthe group consisting of: Berek-type with optical axis essentiallyperpendicular to a surface thereof; non-Berek-type with an optical axisessentially parallel to a surface thereof; zero-order wave plate;zero-order waveplate constructed from two multiple order waveplates;rhomb; polymer; achromatic crystal; and pseudo-achromatic.
 14. Aspectroscopic rotating compensator ellipsometer system as in claim 1, inwhich the dispersive optics is a diffraction grating.
 15. Aspectroscopic rotating compensator ellipsometer system as in claim 14 inwhich said diffraction grating is selected from the group consisting of:“lined”; “blazed”; and “holographic” geometry; said lined geometryconsisting essentially of symetrical alternating lines with depressionstherebetween, and said blazed geometry consisting of alternating rampshaped lines with depressions therebetween, and said holographicgeometry consisting of continuous cosine shaped lines and depressions.16. A spectroscopic rotating compensator ellipsometer system as in claim1, in which the dispersive optics comprises a prism.
 17. A spectroscopicrotating compensator ellipsometer system as in claim 1 which furthercomprises a focusing element after said stage-for supporting a samplesystem and prior to said at least one detector system.
 18. Aspectroscopic rotating compensator ellipsometer system as in claim 1 inwhich compensators are present both before and after said stage forsupporting a sample system, and a selection is made from the groupconsisting of: both said compensators are caused to rotate in use; andone of said compensators is caused to rotate in use.
 19. A spectroscopicrotating compensator ellipsometer system as in claim 1 in which a fiberoptic is present at at least one location selected from the groupconsisting of: between said source of a polychromatic beam ofelectromagnetic radiation and a polarizer; and between said analyzer andsaid dispersive optics and at least one detector system which contains amultiplicity of detector elements.
 20. A spectroscopic rotatingcompensator ellipsometer system as in claim 19 in which a fiber optic ispresent after said analyzer, said fiber optic becoming at leastbifurcated thereby providing a plurality of fiber optic bundles, atleast two of which plurality of at least two bifurcated fiber opticbundles provide input to separate detector systems, each of saidseparate detector systems comprising a dispersion optics and amultiplicity of detector elements, said plurality of fiber optic bundleshaving cross-sectional shapes at ends thereof selected from the group:essentially circular, essentially slit shaped; other than essentiallycircular; and essentially slit shaped.
 21. A spectroscopic ellipsometersystem as in claim 1, in which the compensator comprises a singleelement.
 22. A spectroscopic ellipsometer system as in claim 1, in whichthe compensator comprises at least two per se. zero-order waveplates(MOA) and (MOB), said per se. zero-order waveplates (MOA) and (MOB)having their respective fast axes rotated to a position offset from zeroor ninety degrees with respect to one another, with a nominal valuebeing forty-five degrees.
 23. A spectroscopic ellipsometer system as inclaim 1, in which the compensator comprises a combination of at least afirst (ZO1) and a second (ZO2) effective zero-order wave plate, saidfirst (ZO1) effective zero-order wave plate being comprised of twomultiple order waveplates (MOA1) and (MOB1) which are combined with thefast axes thereof oriented at a nominal ninety degrees to one another,and said second (ZO2) effective zero-order wave plate being comprised oftwo multiple order waveplates (MOA2) and (MOB2) which are combined withthe fast axes thereof oriented at a nominal ninety degrees to oneanother; the fast axes (FAA2) and (FAB2) of the multiple orderwaveplates (MOA2) and (MOB2) in said second effective zero-order waveplate (ZO2) being rotated to a position at a nominal forty-five degreesto the fast axes (FAA1) and (FAB1), respectively, of the multiple orderwaveplates (MOA1) and (MOB1) in said first effective zero-orderwaveplate (ZO1).
 24. A spectroscopic ellipsometer system as in claim 1,in which the compensator comprises at least a first (ZO1) and a second(ZO2) effective zero-order wave plate, said first (ZO1) effectivezero-order wave plate being comprised of two multiple order waveplates(MOA1) and (MOB1) which are combined with the fast axes thereof orientedat a nominal ninety degrees to one another, and said second (ZO2)effective zero-order wave plate being comprised of two multiple orderwaveplates (MOA2) and (MOB2) which are combined with the fast axesthereof oriented at a nominal ninety degrees to one another; the fastaxes (FAA2) and (FAB2) of the multiple order waveplates (MOA2) and(MOB2) in said second effective zero-order wave plate (ZO2) beingrotated to a position away from zero or ninety degrees with respect tothe fast axes (FAA1) and (FAB1), respectively, of the multiple orderwaveplates (MOA1) and (MOB1) in said first effective zero-orderwaveplate (ZO1).
 25. A spectroscopic ellipsometer system as in claim 1,in which the compensator comprises at least one zero-order waveplate,((MOA) or (MOB)), and at least one effective zero-order waveplate,((ZO2) or (ZO1) respectively), said effective zero-order wave plate,((ZO2) or (ZO1)), being comprised of two multiple order waveplates whichare combined with the fast axes thereof oriented at a nominal ninetydegrees to one another, the fast axes of the multiple order waveplatesin said effective zero-order wave plate, ((ZO2) or (ZO1)), being rotatedto a position away from zero or ninety degrees with respect to the fastaxis of the zero-order waveplate, ((MOA) or (MOB)).
 26. A spectroscopicellipsometer system as in claim 1, in which the compensator comprises afirst triangular shaped element, which as viewed in side elevationpresents with first and second sides which project to the left and rightand downward from an upper point, which first triangular shaped elementfirst and second sides have reflective outer surfaces; said retardersystem further comprising a second triangular shaped element which asviewed in side elevation presents with first and second sides whichproject to the left and right and downward from an upper point, saidsecond triangular shaped element being made of sample which providesreflective interfaces on first and second sides inside thereof; saidsecond triangular shaped element being oriented with respect to thefirst triangular shaped element such that the upper point of said secondtriangular shaped element is oriented essentially vertically directlyabove the upper point of said first triangular shaped element; such thatin use an input electromagnetic beam of radiation caused to approach oneof said first and second sides of said first triangular shaped elementalong an essentially horizontally oriented locus, is caused toexternally reflect from an outer surface thereof and travel along alocus which is essentially upwardly vertically oriented, then enter saidsecond triangular shaped element and essentially totally internallyreflect from one of said first and second sides thereof, then proceedalong an essentially horizontal locus and essentially totally internallyreflect from the other of said first and second sides and proceed alongan essentially downward vertically oriented locus, then externallyreflect from the other of said first and second sides of said firsttriangular shaped elements and proceed along an essentially horizontallyoriented locus which is undeviated and undisplaced from the essentiallyhorizontally oriented locus of said input beam of essentiallyhorizontally oriented electromagnetic radiation; with a result beingthat retardation is entered between orthogonal components of said inputelectromagnetic beam of radiation.
 27. A spectroscopic ellipsometersystem as in claim 1, in which the compensator comprises, as viewed inupright side elevation, first and second orientation adjustable mirroredelements which each have reflective surfaces; said compensator systemfurther comprising a third element which, as viewed in upright sideelevation, presents with first and second sides which project to theleft and right and downward from an upper point, said third elementbeing made of sample which provides reflective interfaces on first andsecond sides inside thereof; said third element being oriented withrespect to said first and second orientation adjustable mirroredelements such that in use an input electromagnetic beam of radiationcaused to approach one of said first and second orientation adjustablemirrored elements along an essentially horizontally oriented locus, iscaused to externally reflect therefrom and travel along a locus which isessentially upwardly vertically oriented, then enter said third elementand essentially totally internally reflect from one of said first andsecond sides thereof, then proceed along an essentially horizontal locusand essentially totally internally reflect from the other of said firstand second sides and proceed along an essentially downward verticallyoriented locus, then reflect from the other of said first and secondorientation adjustable mirrored elements and proceed along anessentially horizontally oriented propagation direction locus which isessentially undeviated and undisplaced from the essentially horizontallyoriented propagation direction locus of said input beam of essentiallyhorizontally oriented electromagnetic radiation; with a result beingthat retardation is entered between orthogonal components of said inputelectromagnetic beam of radiation.
 28. A spectroscopic ellipsometersystem as in claim 1, in which the compensator comprises a parallelogramshaped element which, as viewed in side elevation, has top and bottomsides parallel to one another, both said top and bottom sides beingoriented essentially horizontally, said retarder system also havingright and left sides parallel to one another, both said right and leftsides being oriented at an angle to horizontal, said retarder being madeof a sample with an index of refraction greater than that of asurrounding ambient; such that in use an input beam of electromagneticradiation caused to enter a side of said retarder selected from thegroup consisting of: right and left; along an essentially horizontallyoriented locus, is caused to diffracted inside said retarder system andfollow a locus which causes it to essentially totally internally reflectfrom internal interfaces of both said top and bottom sides, and emergefrom said retarder system from a side selected from the group consistingof left and right respectively; along an essentially horizontallyoriented locus which is undeviated and undisplaced from the essentiallyhorizontally oriented locus of said input beam of essentiallyhorizontally oriented electromagnetic radiation; with a result beingthat retardation is entered between orthogonal components of said inputelectromagnetic beam of radiation.
 29. A spectroscopic ellipsometersystem as in claim 1, in which the compensator comprises first andsecond triangular shaped elements, said first triangular shaped element,as viewed in side elevation, presenting with first and second sideswhich project to the left and right and downward from an upper point,said first triangular shaped element further comprising a third sidewhich is oriented essentially horizontally and which is continuous with,and present below said first and second sides; and said secondtriangular shaped element, as viewed in side elevation, presenting withfirst and second sides which project to the left and right and upwardfrom an upper point, said second triangular shaped element furthercomprising a third side which is oriented essentially horizontally andwhich is continuous with, and present above said first and second sides;said first and second triangular shaped elements being positioned sothat a rightmost side of one of said first and second triangular shapedelements is in contact with a leftmost side of the other of said firstand second triangular shaped elements over at least a portion of thelengths thereof; said first and second triangular shaped elements eachbeing made of sample with an index of refraction greater than that of asurrounding ambient; such that in use an input beam of electromagneticradiation caused to enter a side of a triangular shaped element selectedfrom the group consisting of: first and second; not in contact with saidother triangular shape element, is caused to diffracted inside saidretarder and follow a locus which causes it to essentially totallyinternally reflect from internal interfaces of said third sides of eachof said first and second triangular shaped elements, and emerge from aside of said triangular shaped element selected from the groupconsisting of: second and first; not in contact with said othertriangular shape element, along an essentially horizontally orientedlocus which is undeviated and undisplaced from the essentiallyhorizontally oriented locus of said input beam of essentiallyhorizontally oriented electromagnetic radiation; with a result beingthat retardation is entered between orthogonal components of said inputelectromagnetic beam of radiation.
 30. A spectroscopic ellipsometersystem as in claim 1, in which the compensator comprises a triangularshaped element, which as viewed in side elevation presents with firstand second sides which project to the left and right and downward froman upper point, said retarder system further comprising a third sidewhich is oriented essentially horizontally and which is continuous with,and present below said first and second sides; said retarder systembeing made of a sample with an index of refraction greater than that ofa surrounding ambient; such that in use a an input beam ofelectromagnetic radiation caused to enter a side of said retarder systemselected from the group consisting of: first and second; along anessentially horizontally oriented locus, is caused to diffracted insidesaid retarder system and follow a locus which causes it to essentiallytotally internally reflect from internal interface of said third sides,and emerge from said retarder from a side selected from the groupconsisting of second and first respectively; along an essentiallyhorizontally oriented locus which is undeviated and undisplaced from theessentially horizontally oriented locus of said input beam ofessentially horizontally oriented electromagnetic radiation; with aresult being that retardation is entered between orthogonal componentsof said input electromagnetic beam of radiation.
 31. A spectroscopicellipsometer system as in claim 1, in which the compensator comprisesfirst and second Berek-type retarders which each have an optical axesessentially perpendicular to a surface thereof, each of which first andsecond Berek-type retarders has a fast axis, said fast axes in saidfirst and second Berek-type retarders being oriented in an orientationselected from the group consisting of: parallel to one another; andother than parallel to one another; said first and second Berek-typeretarders each presenting with first and second essentially parallelsides, and said first and second Berek-type retarders being oriented, asviewed in side elevation, with first and second sides of one Berek-typeretarder being oriented other than parallel to first and second sides ofthe other Berek-type retarder; such that in use an incident beam ofelectromagnetic radiation is caused to impinge upon one of said firstand second Berek-type retarders on one side thereof, partially transmittherethrough then impinge upon the second Berek-type retarder, on oneside thereof, and partially transmit therethrough such that a polarizedbeam of electromagnetic radiation passing through both of said first andsecond Berek-type retarders emerges from the second thereof in apolarized state with a phase angle between orthogonal components thereinwhich is different than that in the incident beam of electromagneticradiation, and in a propagation direction which is essentiallyundeviated and undisplaced from the incident beam of electromagneticradiation; with a result being that retardation is entered betweenorthogonal components of said input electromagnetic beam of radiation.32. A spectroscopic ellipsometer system as in claim 1, in which thecompensator comprises first and second Berek-type retarders which eachhave an optical axes essentially perpendicular to a surface thereof,each of which first and second Berek-type retarders has a fast axis,said fast axes in said first and second Berek-type retarders beingoriented other than parallel to one another; said first and secondBerek-type retarders each presenting with first and second essentiallyparallel sides, and said first and second Berek-type retarders beingoriented, as viewed in side elevation, with first and second sides ofone Berek-type retarder being oriented other than parallel to first andsecond sides of the other Berek-type retarder; such that in use anincident beam of electromagnetic radiation is caused to impinge upon oneof said first and second Berek-type retarders on one side thereof,partially transmit therethrough then impinge upon the second Berek-typeretarder, on one side thereof, and partially transmit therethrough suchthat a polarized beam of electromagnetic radiation passing through bothof said first and second Berek-type retarders emerges from the secondthereof in a polarized state with a phase angle between orthogonalcomponents therein which is different than that in the incident beam ofelectromagnetic radiation, and in a propagation direction which isessentially undeviated and undisplaced from the incident beam ofelectromagnetic radiation, said spectroscopic ellipsometer/polarimetersystem further comprising third and fourth Berek-type retarders whicheach have an optical axes essentially perpendicular to a surfacethereof, each of which third and fourth Berek-type retarders has a fastaxis, said fast axes in said third and fourth Berek-type retarders beingoriented other than parallel to one another, said third and fourthBerek-type retarders each presenting with first and second essentiallyparallel sides, and said third and fourth Berek-type retarders beingoriented, as viewed in side elevation, with first and second sides ofone of said third and fourth Berek-type retarders being oriented otherthan parallel to first and second sides of said fourth Berek-typeretarder; such that in use an incident beam of electromagnetic radiationexiting said second Berek-type retarder is caused to impinge upon saidthird Berek-type retarder on one side thereof, partially transmittherethrough then impinge upon said fourth Berek-type retarder on oneside thereof, and partially transmit therethrough such that a polarizedbeam of electromagnetic radiation passing through said first, second,third and fourth Berek-type retarders emerges from the fourth thereof ina polarized state with a phase angle between orthogonal componentstherein which is different than that in the incident beam ofelectromagnetic radiation caused to impinge upon the first side of saidfirst Berek-type retarder, and in a direction which is essentiallyundeviated and undisplaced from said incident beam of electromagneticradiation; with a result being that retardation is entered betweenorthogonal components of said input electromagnetic beam of radiation.33. A spectroscopic ellipsometer system as in claim 1, in which thecompensator comprises first, second, third and fourth Berek-typeretarders which each have an optical axes essentially perpendicular to asurface thereof, each of which first and second Berek-type retarders hasa fast axis, said fast axes in said first and second Berek-typeretarders being oriented essentially parallel to one another; said firstand second Berek-type retarders each presenting with first and secondessentially parallel sides, and said first and second Berek-typeretarders being oriented, as viewed in side elevation, with first andsecond sides of one Berek-type retarder being oriented other thanparallel to first and second sides of the other Berek-type retarder;such that in use an incident beam of electromagnetic radiation is causedto impinge upon one of said first and second Berek-type retarders on oneside thereof, partially transmit therethrough then impinge upon thesecond Berek-type retarder, on one side thereof, and partially transmittherethrough such that a polarized beam of electromagnetic radiationpassing through both of said first and second Berek-type retardersemerges from the second thereof in a polarized state with a phase anglebetween orthogonal components therein which is different than that inthe incident beam of electromagnetic radiation, and in a propagationdirection which is essentially undeviated and undisplaced from theincident beam of electromagnetic radiation; each of which third andfourth Berek-type retarders has a fast axis, said fast axes in saidthird and fourth Berek-type retarders being oriented essentiallyparallel to one another but other than parallel to the fast axes of saidfirst and second Berek-type retarders, said third and fourth Berek-typeretarders each presenting with first and second essentially parallelsides, and said third and fourth Berek-type retarders being oriented, asviewed in side elevation, with first and second sides of one of saidthird and fourth Berek-type retarders being oriented other than parallelto first and second sides of said fourth Berek-type retarder; such thatin use an incident beam of electromagnetic radiation exiting said secondBerek-type retarder is caused to impinge upon said third Berek-typeretarder on one side thereof, partially transmit therethrough thenimpinge upon said fourth Berek-type retarder on one side thereof, andpartially transmit therethrough such that a polarized beam ofelectromagnetic radiation passing through said first, second, third andfourth Berek-type retarders emerges from the fourth thereof in apolarized state with a phase angle between orthogonal components thereinwhich is different than that in the incident beam of electromagneticradiation caused to impinge upon the first side of said first Berek-typeretarder, and in a direction which is essentially undeviated andundisplaced from said incident beam of electromagnetic radiation; with aresult being that retardation is entered between orthogonal componentsof said input electromagnetic beam of radiation.
 34. A spectroscopicellipsometer system as in claim 1, in which electromagnetic radiationfrom or to at least one selection from the group consisting of: thesource of polychromatic electromagnetic radiation; and the multi-elementspectroscopic detector system; is via fiber optics.
 35. A method ofprocessing an electromagnetic beam in a rotating compensatorellipsometers comprising the steps of: a. providing a rotatingcompensator ellipsometer system which comprises a source of apolychromatic beam of electromagnetic radiation, a polarizer, a stagefor supporting a sample system, an analyzer, a dispersive optics and atleast one detector system which contains a multiplicity of detectorelements, said spectroscopic rotating compensator ellipsometer systemfurther comprising at least one compensator(s) positioned at a locationselected from the group consisting of: before said stage for supportinga sample system; and after said stage for supporting a sample system;and both before and after said stage for supporting a sample system;such that when said spectroscopic rotating compensator ellipsometersystem is used to investigate a sample system present on said stage forsupporting a sample system, said analyzer and polarizer are maintainedessentially fixed in position and at least one of said at least onecompensator(s) is caused to continuously rotate while a polychromaticbeam of electromagnetic radiation produced by said source of apolychromatic beam of electromagnetic radiation is caused to passthrough said polarizer and said compensator(s), said polychromatic beamof electromagnetic radiation being also caused to interact with saidsample system, pass through said analyzer and interact with saiddispersive optics such that a multiplicity of essentially singlewavelengths are caused to simultaneously enter a correspondingmultiplicity of detector elements in said at least one detector system;b. said method further comprising placing at least one spatial filter(s)such that said electromagnetic beam passes therethrough, said spatialfilter sequentially comprising: beam converging at least one lens and/ormirror; diaphram with a pin hole therein located near the focal lengthof said beam converging at least one lens and/or mirror; and beamcollimating at least one lens and/or mirror; such that in use anelectromagnetic beam which is caused to pass through said aperture,become focused on and at least partially pass through said pin hole insaid diaphram by said at least one beam converging lens and/or mirror,and become recollimated by said second beam collimating at least onelens and/or mirror, the purpose being to eliminate a radially outerannulus of said electromagentic beam, said outer annulus being comprisedof low intensity level irregular content; and c. causing said source ofa polychromatic beam of electromagnetic radiation to provide a beam ofelectromagnetic radiation.
 36. A method of processing electromagneticbeams in rotating compensator ellipsometers, as in claim 35; in whichthe step of placing at least one spatial filter(s) such that saidelectromagnetic beam passes therethrough comprises placing said spatialfilter in selection from the group consisting of: before said stage forsupporting a sample system; and after said stage for supporting a samplesystem; and both before and after said stage for supporting a samplesystem.
 37. A spectroscopic rotating compensator ellipsometer system asin claim 35 wherein the step of placing at least one spatial filter(s)such that said electromagnetic beam passes therethrough comprisesplacing a spatial filter at a location selected from the groupconsisting of: between the source and polarizer; between the polarizerand a compensator; between a compensator and sample system; between thesample system and a compensator; between a compensator and analyzer; andbetween the analyzer and detector.